Adapt bwc version after backport (bis)

Relates #34225

Author: jimczi

server/src/main/java/org/elasticsearch/search/fetch/FetchPhase.java

@@ -377,7 +377,7 @@ private SearchHit.NestedIdentity getInternalNestedIdentity(SearchContext context
             BitSet parentBits = context.bitsetFilterCache().getBitSetProducer(parentFilter).getBitSet(subReaderContext);
 
             int offset = 0;
-            if (indexSettings.getIndexVersionCreated().onOrAfter(Version.V_7_0_0_alpha1)) {
+            if (indexSettings.getIndexVersionCreated().onOrAfter(Version.V_6_5_0)) {
                 /**
                  * Starts from the previous parent and finds the offset of the
                  * <code>nestedSubDocID</code> within the nested children. Nested documents