fix nested single clause boolean queries

Signed-off-by: Sawan Srivastava <[email protected]>

Author: sawansri

server/src/main/java/org/opensearch/search/approximate/ApproximateBooleanQuery.java

@@ -78,6 +78,9 @@ public Query rewrite(IndexSearcher indexSearcher) throws IOException {
 
             // If the single clause is an ApproximateScoreQuery, set its context
             if (clauseQuery instanceof ApproximateScoreQuery approximateQuery) {
+                if (approximateQuery.getApproximationQuery() instanceof ApproximateBooleanQuery nestedBool) {
+                    return nestedBool.rewrite(indexSearcher);
+                }
                 return approximateQuery;
             }