[ML] Improve assertion error msg in ResetJobIT (#89653)

This adds an error message that reveals the audit messages
if the assertion that the last msg is about resetting the job
fails.

Relates #89644

x-pack/plugin/ml/qa/native-multi-node-tests/src/javaRestTest/java/org/elasticsearch/xpack/ml/integration/ResetJobIT.java

@@ -69,7 +69,7 @@ public void testReset() throws IOException {
 
         List<String> auditMessages = fetchAllAuditMessages(job.getId());
         assertThat(auditMessages.isEmpty(), is(false));
-        assertThat(auditMessages.get(auditMessages.size() - 1), equalTo("Job has been reset"));
+        assertThat("Audit messages: " + auditMessages, auditMessages.get(auditMessages.size() - 1), equalTo("Job has been reset"));
     }
 
     private Job.Builder createJob(String jobId, TimeValue bucketSpan) {