Fix flaky test SimpleProducerConsumerTest.testActiveAndInActiveConsum…

…erEntryCacheBehavior (apache#10556)

Fixes apache#10555

pulsar-broker/src/test/java/org/apache/pulsar/client/api/SimpleProducerConsumerTest.java

@@ -1028,7 +1028,7 @@ public void testActiveAndInActiveConsumerEntryCacheBehavior() throws Exception {
         msg = subscriber1.receive(RECEIVE_TIMEOUT_SECONDS, TimeUnit.SECONDS);
 
         // Verify: as active-subscriber2 has not consumed messages: EntryCache must have those entries in cache
-        assertTrue(entryCache.getSize() != 0);
+        Awaitility.await().untilAsserted(() -> assertNotEquals(entryCache.getSize(), 0));
 
         // 3.b Close subscriber2: which will trigger cache to clear the cache
         subscriber2.close();