Enable bwc tests now that #74226 has been to 7.x branch. (#75968)

build.gradle

@@ -145,9 +145,9 @@ tasks.register("verifyVersions") {
  * after the backport of the backcompat code is complete.
  */
 
-boolean bwc_tests_enabled = false
+boolean bwc_tests_enabled = true
 // place a PR link here when committing bwc changes:
-String bwc_tests_disabled_issue = "https://github.com/elastic/elasticsearch/pull/74226"
+String bwc_tests_disabled_issue = ""
 /*
  * FIPS 140-2 behavior was fixed in 7.11.0. Before that there is no way to run elasticsearch in a
  * JVM that is properly configured to be in fips mode with BCFIPS. For now we need to disable

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/DeprecationIssue.java

@@ -82,7 +82,7 @@ public DeprecationIssue(StreamInput in) throws IOException {
         message = in.readString();
         url = in.readString();
         details = in.readOptionalString();
-        resolveDuringRollingUpgrade = in.getVersion().onOrAfter(Version.V_8_0_0) && in.readBoolean();
+        resolveDuringRollingUpgrade = in.getVersion().onOrAfter(Version.V_7_15_0) && in.readBoolean();
         meta = in.getVersion().onOrAfter(Version.V_7_14_0) ? in.readMap() : null;
     }
 
@@ -123,7 +123,7 @@ public void writeTo(StreamOutput out) throws IOException {
         out.writeString(message);
         out.writeString(url);
         out.writeOptionalString(details);
-        if (out.getVersion().onOrAfter(Version.V_8_0_0)) {
+        if (out.getVersion().onOrAfter(Version.V_7_15_0)) {
             out.writeBoolean(resolveDuringRollingUpgrade);
         }
         if (out.getVersion().onOrAfter(Version.V_7_14_0)) {