tweak test

Signed-off-by: Peter Alfonsi <petealft@amazon.com>

Author: Peter Alfonsi

server/src/internalClusterTest/java/org/opensearch/indices/IndicesRequestCacheIT.java

@@ -864,7 +864,10 @@ public Weight createWeight(IndexSearcher searcher, ScoreMode scoreMode, float bo
     }
 
     public void testMappingUpdateClearsCache() throws Exception {
-        Client client = client();
+        String node = internalCluster().startNode(
+            Settings.builder().put(IndicesRequestCache.INDICES_REQUEST_CACHE_CLEANUP_INTERVAL_SETTING_KEY, TimeValue.timeValueMillis(1))
+        ); // Set IRC cleanup frequency low to ensure we don't get false positives when we check the cache hasn't been cleared
+        Client client = client(node);
         String index = "index";
         String field = "k";
         assertAcked(