Remove trace logging for ML native multi-node tests

This trace logging looks like it was copy/pasted from another test,
where the logging in that test was only added to investigate a test
failure. This commit removes the trace logging.

x-pack/plugin/ml/qa/native-multi-node-tests/build.gradle

@@ -42,7 +42,6 @@ testClusters.integTest {
     setting 'xpack.security.enabled', 'true'
     setting 'xpack.ml.enabled', 'true'
     setting 'xpack.watcher.enabled', 'false'
-    setting 'logger.org.elasticsearch.xpack.ml.datafeed', 'TRACE'
     setting 'xpack.monitoring.enabled', 'false'
     setting 'xpack.security.authc.token.enabled', 'true'
     setting 'xpack.security.transport.ssl.enabled', 'true'