Update version in SearchHits transport serialization

Now that #36555 is backported to 6.x, the version in the transport serialization conditionals for sort and collapse info can be updated to 6.6.0

Author: javanna

server/src/main/java/org/elasticsearch/search/SearchHits.java

@@ -243,8 +243,7 @@ public void readFrom(StreamInput in) throws IOException {
                 hits[i] = SearchHit.readSearchHit(in);
             }
         }
-        //TODO update version once backported
-        if (in.getVersion().onOrAfter(Version.V_7_0_0)) {
+        if (in.getVersion().onOrAfter(Version.V_6_6_0)) {
             sortFields = in.readOptionalArray(Lucene::readSortField, SortField[]::new);
             collapseField = in.readOptionalString();
             collapseValues = in.readOptionalArray(Lucene::readSortValue, Object[]::new);
@@ -265,8 +264,7 @@ public void writeTo(StreamOutput out) throws IOException {
                 hit.writeTo(out);
             }
         }
-        //TODO update version once backported
-        if (out.getVersion().onOrAfter(Version.V_7_0_0)) {
+        if (out.getVersion().onOrAfter(Version.V_6_6_0)) {
             out.writeOptionalArray(Lucene::writeSortField, sortFields);
             out.writeOptionalString(collapseField);
             out.writeOptionalArray(Lucene::writeSortValue, collapseValues);

server/src/test/java/org/elasticsearch/search/SearchHitsTests.java

@@ -271,10 +271,9 @@ public void testFromXContentWithShards() throws IOException {
         }
     }
 
-    //TODO rename method and adapt versions after backport
-    public void testReadFromPre70() throws IOException {
+    public void testReadFromPre6_6_0() throws IOException {
         try (StreamInput in = StreamInput.wrap(Base64.getDecoder().decode("AQC/gAAAAAA="))) {
-            in.setVersion(VersionUtils.randomVersionBetween(random(), Version.V_6_0_0, VersionUtils.getPreviousVersion(Version.V_7_0_0)));
+            in.setVersion(VersionUtils.randomVersionBetween(random(), Version.V_6_0_0, VersionUtils.getPreviousVersion(Version.V_6_6_0)));
             SearchHits searchHits = new SearchHits();
             searchHits.readFrom(in);
             assertEquals(0, searchHits.getHits().length);
@@ -288,9 +287,8 @@ public void testReadFromPre70() throws IOException {
         }
     }
 
-    //TODO rename method and adapt versions after backport
-    public void testSerializationPre70() throws IOException {
-        Version version = VersionUtils.randomVersionBetween(random(), Version.V_6_0_0, VersionUtils.getPreviousVersion(Version.V_7_0_0));
+    public void testSerializationPre6_6_0() throws IOException {
+        Version version = VersionUtils.randomVersionBetween(random(), Version.V_6_0_0, VersionUtils.getPreviousVersion(Version.V_6_6_0));
         SearchHits original = createTestItem(randomFrom(XContentType.values()), false, true, TotalHits.Relation.EQUAL_TO);
         SearchHits deserialized = copyInstance(original, version);
         assertArrayEquals(original.getHits(), deserialized.getHits());