Adjust version compatiblity after backport (#57805)

For the ml delete expired data request changes in #57337

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/DeleteExpiredDataAction.java

@@ -71,7 +71,7 @@ public class DeleteExpiredDataAction extends ActionType<DeleteExpiredDataAction.
                 this.requestsPerSecond = null;
                 this.timeout = null;
             }
-            if (in.getVersion().onOrAfter(Version.V_8_0_0)) { // TODO BWC for V_7_9_0
+            if (in.getVersion().onOrAfter(Version.V_7_9_0)) {
                 jobId = in.readString();
             }
         }
@@ -135,7 +135,7 @@ public class DeleteExpiredDataAction extends ActionType<DeleteExpiredDataAction.
                 out.writeOptionalFloat(requestsPerSecond);
                 out.writeOptionalTimeValue(timeout);
             }
-            if (out.getVersion().onOrAfter(Version.V_8_0_0)) {  // TODO BWC for V_7_9_0
+            if (out.getVersion().onOrAfter(Version.V_7_9_0)) {
                 out.writeString(jobId);
             }
         }

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/ml/action/DeleteExpiredDataActionRequestTests.java

@@ -38,7 +38,7 @@ public class DeleteExpiredDataActionRequestTests extends AbstractBWCWireSerializ
         if (version.before(Version.V_7_8_0)) {
             return new Request();
         }
-        if (version.before(Version.V_8_0_0)) {  // TODO make V_7_9_0
+        if (version.before(Version.V_7_9_0)) {
             Request request = new Request();
             request.setRequestsPerSecond(instance.getRequestsPerSecond());
             request.setTimeout(instance.getTimeout());