Stop copying bucket list when doing desc sort (#110439)

No need to copy here, the list is freshly allocated for us in 100% of
cases here and we're not copying when sorting either.

server/src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalDateHistogram.java

@@ -497,9 +497,7 @@ public final class InternalDateHistogram extends InternalMultiBucketAggregation<
                     }
                     if (InternalOrder.isKeyDesc(order)) {
                         // we just need to reverse here...
-                        List<Bucket> reverse = new ArrayList<>(reducedBuckets);
-                        Collections.reverse(reverse);
-                        reducedBuckets = reverse;
+                        Collections.reverse(reducedBuckets);
                     } else if (InternalOrder.isKeyAsc(order) == false) {
                         // nothing to do when sorting by key ascending, as data is already sorted since shards return
                         // sorted buckets and the merge-sort performed by reduceBuckets maintains order.

server/src/main/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalHistogram.java

@@ -448,9 +448,7 @@ public class InternalHistogram extends InternalMultiBucketAggregation<InternalHi
                     }
                     if (InternalOrder.isKeyDesc(order)) {
                         // we just need to reverse here...
-                        List<Bucket> reverse = new ArrayList<>(reducedBuckets);
-                        Collections.reverse(reverse);
-                        reducedBuckets = reverse;
+                        Collections.reverse(reducedBuckets);
                     } else if (InternalOrder.isKeyAsc(order) == false) {
                         // nothing to do when sorting by key ascending, as data is already sorted since shards return
                         // sorted buckets and the merge-sort performed by reduceBuckets maintains order.