[ML] Removing last traces of system_annotations_retention_days (#76115)

* [ML] Removing last traces of system_annotations_retention_days

Remove the last bits of code after the backport PR (#76113)
is merged.

Followup to #76096

* unmute bwc tests

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>
Co-authored-by: Benjamin Trent <ben.w.trent@gmail.com>

build.gradle

@@ -145,9 +145,9 @@ tasks.register("verifyVersions") {
  * after the backport of the backcompat code is complete.
  */
 
-boolean bwc_tests_enabled = false
+boolean bwc_tests_enabled = true
 // place a PR link here when committing bwc changes:
-String bwc_tests_disabled_issue = "https://github.com/elastic/elasticsearch/pull/76096"
+String bwc_tests_disabled_issue = ""
 /*
  * FIPS 140-2 behavior was fixed in 7.11.0. Before that there is no way to run elasticsearch in a
  * JVM that is properly configured to be in fips mode with BCFIPS. For now we need to disable

x-pack/plugin/build.gradle

@@ -145,13 +145,6 @@ def v7compatibilityNotSupportedTests = {
     'rollup/start_job/Test start job twice',
     'service_accounts/10_basic/Test service account tokens', // https://github.com/elastic/elasticsearch/pull/75200
 
-    // temporarily muted awaiting backport of https://github.com/elastic/elasticsearch/pull/76097
-    'ml/delete_expired_data/Test delete expired data with body parameters',
-    'ml/delete_expired_data/Test delete expired data with no body',
-    'ml/delete_expired_data/Test delete expired data with path parameters',
-    'ml/delete_expired_data/Test delete expired data with unknown job id',
-    'ml/jobs_crud/Test update job',
-
     // a type field was added to cat.ml_trained_models #73660, this is a backwards compatible change.
     // still this is a cat api, and we don't support them with rest api compatibility. (the test would be very hard to transform too)
     'ml/trained_model_cat_apis/Test cat trained models'

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/job/config/Job.java

@@ -244,9 +244,6 @@ public class Job extends AbstractDiffable<Job> implements Writeable, ToXContentO
         modelSnapshotRetentionDays = in.readOptionalLong();
         dailyModelSnapshotRetentionAfterDays = in.readOptionalLong();
         resultsRetentionDays = in.readOptionalLong();
-        if (in.getVersion().onOrAfter(Version.V_7_15_0) && in.getVersion().before(Version.V_8_0_0)) {
-            /* systemAnnotationsRetentionDays = */ in.readOptionalLong();
-        }
         Map<String, Object> readCustomSettings = in.readMap();
         customSettings = readCustomSettings == null ? null : Collections.unmodifiableMap(readCustomSettings);
         modelSnapshotId = in.readOptionalString();
@@ -529,9 +526,6 @@ public class Job extends AbstractDiffable<Job> implements Writeable, ToXContentO
         out.writeOptionalLong(modelSnapshotRetentionDays);
         out.writeOptionalLong(dailyModelSnapshotRetentionAfterDays);
         out.writeOptionalLong(resultsRetentionDays);
-        if (out.getVersion().onOrAfter(Version.V_7_15_0) && out.getVersion().before(Version.V_8_0_0)) {
-            out.writeOptionalLong(resultsRetentionDays);
-        }
         out.writeMap(customSettings);
         out.writeOptionalString(modelSnapshotId);
         if (modelSnapshotMinVersion != null) {
@@ -779,9 +773,6 @@ public class Job extends AbstractDiffable<Job> implements Writeable, ToXContentO
             modelSnapshotRetentionDays = in.readOptionalLong();
             dailyModelSnapshotRetentionAfterDays = in.readOptionalLong();
             resultsRetentionDays = in.readOptionalLong();
-            if (in.getVersion().onOrAfter(Version.V_7_15_0) && in.getVersion().before(Version.V_8_0_0)) {
-                /* systemAnnotationsRetentionDays = */ in.readOptionalLong();
-            }
             customSettings = in.readMap();
             modelSnapshotId = in.readOptionalString();
             if (in.readBoolean()) {
@@ -1009,9 +1000,6 @@ public class Job extends AbstractDiffable<Job> implements Writeable, ToXContentO
             out.writeOptionalLong(modelSnapshotRetentionDays);
             out.writeOptionalLong(dailyModelSnapshotRetentionAfterDays);
             out.writeOptionalLong(resultsRetentionDays);
-            if (out.getVersion().onOrAfter(Version.V_7_15_0) && out.getVersion().before(Version.V_8_0_0)) {
-                out.writeOptionalLong(resultsRetentionDays);
-            }
             out.writeMap(customSettings);
             out.writeOptionalString(modelSnapshotId);
             if (modelSnapshotMinVersion != null) {

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/job/config/JobUpdate.java

@@ -143,9 +143,6 @@ public class JobUpdate implements Writeable, ToXContentObject {
         modelSnapshotRetentionDays = in.readOptionalLong();
         dailyModelSnapshotRetentionAfterDays = in.readOptionalLong();
         resultsRetentionDays = in.readOptionalLong();
-        if (in.getVersion().onOrAfter(Version.V_7_15_0) && in.getVersion().before(Version.V_8_0_0)) {
-            /* systemAnnotationsRetentionDays = */ in.readOptionalLong();
-        }
         if (in.readBoolean()) {
             categorizationFilters = in.readStringList();
         } else {
@@ -192,9 +189,6 @@ public class JobUpdate implements Writeable, ToXContentObject {
         out.writeOptionalLong(modelSnapshotRetentionDays);
         out.writeOptionalLong(dailyModelSnapshotRetentionAfterDays);
         out.writeOptionalLong(resultsRetentionDays);
-        if (out.getVersion().onOrAfter(Version.V_7_15_0) && out.getVersion().before(Version.V_8_0_0)) {
-            out.writeOptionalLong(resultsRetentionDays);
-        }
         out.writeBoolean(categorizationFilters != null);
         if (categorizationFilters != null) {
             out.writeStringCollection(categorizationFilters);