Fix nested agg test

I accidentally allowed the test framework to double-wrap a reader that
we rely on being only singly wrapped. Lame.

closes elastic#56529

test/framework/src/main/java/org/elasticsearch/search/aggregations/AggregatorTestCase.java

@@ -555,8 +555,14 @@ protected <T extends AggregationBuilder, V extends InternalAggregation> void tes
             buildIndex.accept(indexWriter);
             indexWriter.close();
 
-            try (IndexReader indexReader = wrapDirectoryReader(DirectoryReader.open(directory))) {
-                IndexSearcher indexSearcher = newSearcher(indexReader, true, true);
+            try (DirectoryReader unwrapped = DirectoryReader.open(directory);
+                    IndexReader indexReader = wrapDirectoryReader(unwrapped)) {
+                /*
+                 * Only allow the randomized testing to wrap the reader if
+                 * the test didn't explicitly wrap the reader.
+                 */
+                boolean maybeWrap = unwrapped == indexReader;
+                IndexSearcher indexSearcher = newSearcher(indexReader, maybeWrap, true);
 
                 V agg = searchAndReduce(indexSearcher, query, aggregationBuilder, fieldTypes);
                 verify.accept(agg);