Delegating nextDoc to advance as previous assumption doesn't hold with current ConstantScoreSupplier

Signed-off-by: expani <[email protected]>

Author: expani

server/src/main/java/org/opensearch/search/aggregations/metrics/CardinalityAggregator.java

@@ -452,9 +452,8 @@ public int advance(int target) throws IOException {
         }
 
         @Override
-        public int nextDoc() {
-            // don't expect this to be called based on its usage in DefaultBulkScorer
-            throw new UnsupportedOperationException();
+        public int nextDoc() throws IOException {
+            return advance(slowDocId + 1);
         }
 
         @Override