More copywriting tweaks around the Khepri feature flag

Per discussion with most of the core team.

deps/rabbit/src/rabbit_core_ff.erl

@@ -129,7 +129,7 @@
 
 -rabbit_feature_flag(
    {khepri_db,
-    #{desc          => "New Raft-based metadata store",
+    #{desc          => "New Raft-based metadata store. Fully supported as of RabbitMQ 4.0",
       doc_url       => "", %% TODO
       stability     => experimental,
       depends_on    => [feature_flags_v2,

deps/rabbitmq_management/priv/www/js/tmpl/feature-flags.ejs

@@ -83,12 +83,13 @@
 
 
 <div class="section">
-  <h2>Experimental Feature Flags</h2>
+  <h2>Opt-in Feature Flags</h2>
   <div class="hider">
 <% if (feature_flags.length > 0) { %>
 <p class="warning">
-  Feature flags listed below are experimental (maturing). They can be enabled in production deployments
-  after careful consideration and testing in non-production environments.
+These feature flags opt-in.
+
+These flags can be enabled in production deployments after an appropriate amount of testing in non-production environments.
 </p>
 <table class="list">
   <thead>
@@ -120,7 +121,7 @@
            <% if (feature_flag.state == "disabled") { %>
 	      <div>
               <input id="<%= feature_flag.name %>" type="checkbox" class="riskCheckbox" onclick="this.parentNode.querySelector('.enable-feature-flag input[type=submit]').disabled = !this.checked;">
-              <label for="<%= feature_flag.name %>">I understand the potential risks and want to enable this feature flag</label><br>
+              <label for="<%= feature_flag.name %>">I understand that once enabled, this feature flag cannot be disabled</label><br>
 	      <br>
               <form action="#/feature-flags-enable" method="put" style="display: inline-block" class="enable-feature-flag">
               <input type="hidden" name="name" value="<%= fmt_string(feature_flag.name) %>"/>