Reenable BwC Tests after Merging #59514 (#59568)

Now that #59514 has been merged we can reenable BwC tests.

build.gradle

@@ -174,8 +174,8 @@ tasks.register("verifyVersions") {
  * after the backport of the backcompat code is complete.
  */
 
-boolean bwc_tests_enabled = false
-final String bwc_tests_disabled_issue = "https://github.com/elastic/elasticsearch/pull/59514" /* place a PR link here when committing bwc changes */
+boolean bwc_tests_enabled = true
+final String bwc_tests_disabled_issue = "" /* 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/snapshots/SnapshotsService.java

@@ -123,7 +123,7 @@ public class SnapshotsService extends AbstractLifecycleComponent implements Clus
 
     public static final Version SHARD_GEN_IN_REPO_DATA_VERSION = Version.V_7_6_0;
 
-    public static final Version INDEX_GEN_IN_REPO_DATA_VERSION = Version.V_8_0_0;
+    public static final Version INDEX_GEN_IN_REPO_DATA_VERSION = Version.V_7_9_0;
 
     public static final Version OLD_SNAPSHOT_FORMAT = Version.V_7_5_0;