Fix TophitsAggregatorTests

It needs a DirectoryReader so it has to be careful.

Closes #22818

Author: nik9000

core/src/test/java/org/elasticsearch/search/aggregations/metrics/tophits/TopHitsAggregatorTests.java

@@ -130,7 +130,8 @@ private Aggregation testCase(Query query, AggregationBuilder builder) throws IOE
         iw.close();
 
         IndexReader indexReader = DirectoryReader.open(directory);
-        IndexSearcher indexSearcher = newSearcher(indexReader, true, true);
+        // We do not use LuceneTestCase.newSearcher because we need a DirectoryReader for "testInsideTerms"
+        IndexSearcher indexSearcher = new IndexSearcher(indexReader);
 
         Aggregation result = searchAndReduce(indexSearcher, query, builder, STRING_FIELD_TYPE);
         indexReader.close();