testRecoveryAfterPrimaryPromotion shouldn't flush the replica with extra operations

We don't yet have lucene rollbacks, so we can't bake those in

core/src/test/java/org/elasticsearch/index/replication/RecoveryDuringReplicationTests.java

@@ -186,7 +186,7 @@ public class RecoveryDuringReplicationTests extends ESIndexLevelReplicationTestC
             totalDocs += shards.indexDocs(randomIntBetween(0, 5));
 
             if (randomBoolean()) {
-                shards.flush();
+                newPrimary.flush(new FlushRequest());
             }
 
             oldPrimary.close("demoted", false);