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

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

@@ -186,7 +186,6 @@ public class MonitoringIT extends ESSingleNodeTestCase {
      * 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/elasticsearch/issues/29880")
     public void testMonitoringService() throws Exception {
         final boolean createAPMIndex = randomBoolean();
         final String indexName = createAPMIndex ? "apm-2017.11.06" : "books";