Reenable MonitoringIT#testMonitoringService.

When discussing this test, it made little sense that testMonitoringService
would fail but not testMonitoringBulk given their similarity. So we argeed to
enable it again.

Relates #29880

Author: jpountz

x-pack/plugin/monitoring/src/test/java/org/elasticsearch/xpack/monitoring/integration/MonitoringIT.java

@@ -187,7 +187,6 @@ public void testMonitoringBulk() throws Exception {
      * This test waits for the monitoring service to collect monitoring documents and then checks that all expected documents
      * have been indexed with the expected information.
      */
-    @AwaitsFix(bugUrl = "https://github.com/elastic/x-pack-elasticsearch/issues/4150")
     @SuppressWarnings("unchecked")
     public void testMonitoringService() throws Exception {
         final boolean createAPMIndex = randomBoolean();