Adapt InternalComposite serialization after backport (#50352)

This commit adapts the version checks of the InternalComposite
serialization after the backport of #50272.
Note that this pr disables bwc tests since #50272 is not merged yet.

build.gradle

@@ -205,8 +205,8 @@ task verifyVersions {
  * after the backport of the backcompat code is complete.
  */
 
-boolean bwc_tests_enabled = true
-final String bwc_tests_disabled_issue = "" /* place a PR link here when committing bwc changes */
+boolean bwc_tests_enabled = false
+final String bwc_tests_disabled_issue = "https://github.com/elastic/elasticsearch/pull/50272" /* place a PR link here when committing bwc changes */
 if (bwc_tests_enabled == false) {
   if (bwc_tests_disabled_issue.isEmpty()) {
     throw new GradleException("bwc_tests_disabled_issue must be set when bwc_tests_enabled == false")

server/src/main/java/org/elasticsearch/search/aggregations/bucket/composite/InternalComposite.java

@@ -80,7 +80,7 @@ public class InternalComposite
         this.reverseMuls = in.readIntArray();
         this.buckets = in.readList((input) -> new InternalBucket(input, sourceNames, formats, reverseMuls));
         this.afterKey = in.readOptionalWriteable(CompositeKey::new);
-        this.earlyTerminated = in.getVersion().onOrAfter(Version.V_8_0_0) ? in.readBoolean() : false;
+        this.earlyTerminated = in.getVersion().onOrAfter(Version.V_7_6_0) ? in.readBoolean() : false;
     }
 
     @Override
@@ -93,7 +93,7 @@ public class InternalComposite
         out.writeIntArray(reverseMuls);
         out.writeList(buckets);
         out.writeOptionalWriteable(afterKey);
-        if (out.getVersion().onOrAfter(Version.V_8_0_0)) {
+        if (out.getVersion().onOrAfter(Version.V_7_6_0)) {
             out.writeBoolean(earlyTerminated);
         }
     }