Re-enable BwC Tests (#52110)

Reenabling BwC Tests now that #52108 is merged.

build.gradle

@@ -215,8 +215,8 @@ task 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/52108" /* 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/cluster/routing/RecoverySource.java

@@ -229,7 +229,7 @@ public SnapshotRecoverySource(String restoreUUID, Snapshot snapshot, Version ver
             restoreUUID = in.readString();
             snapshot = new Snapshot(in);
             version = Version.readVersion(in);
-            if (in.getVersion().onOrAfter(Version.V_8_0_0)) {
+            if (in.getVersion().onOrAfter(Version.V_7_7_0)) {
                 index = new IndexId(in);
             } else {
                 index = new IndexId(in.readString(), IndexMetaData.INDEX_UUID_NA_VALUE);
@@ -263,7 +263,7 @@ protected void writeAdditionalFields(StreamOutput out) throws IOException {
             out.writeString(restoreUUID);
             snapshot.writeTo(out);
             Version.writeVersion(version, out);
-            if (out.getVersion().onOrAfter(Version.V_8_0_0)) {
+            if (out.getVersion().onOrAfter(Version.V_7_7_0)) {
                 index.writeTo(out);
             } else {
                 out.writeString(index.getName());