Add compileOnly dependency on JSR-305 annotations for Reactor

After the upgrade to Selenium 4.33.0 in commit 1051592ae8, the
spring-test module began to fail as follows.

/home/runner/.gradle/caches/modules-2/files-2.1/io.projectreactor/reactor-core/3.8.0-M4/3195c7882f5833915a74ee18d58857cabc29b4c6/reactor-core-3.8.0-M4.jar(/reactor/util/annotation/Nullable.class):
  warning: Cannot find annotation method 'when()' in type 'Nonnull':
    class file for javax.annotation.Nonnull not found
warning: unknown enum constant When.MAYBE
  reason: class file for javax.annotation.meta.When not found
error: warnings found and -Werror specified
1 error
2 warnings

To address that, this commit introduces a compileOnly dependency on
"com.google.code.findbugs:jsr305".

spring-test/spring-test.gradle

@@ -4,6 +4,7 @@ apply plugin: "kotlin"
 
 dependencies {
 	api(project(":spring-core"))
+	compileOnly("com.google.code.findbugs:jsr305") // for Reactor
 	optional(project(":spring-aop"))
 	optional(project(":spring-beans"))
 	optional(project(":spring-context"))