Fix ambiguous VisibleForTesting import in VenicePushJob

Remove duplicate Guava VisibleForTesting import that conflicts with
the existing Venice VisibleForTesting annotation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: pthirun

clients/venice-push-job/src/main/java/com/linkedin/venice/hadoop/VenicePushJob.java

@@ -83,7 +83,6 @@
 import static com.linkedin.venice.vpj.VenicePushJobConstants.VENICE_DISCOVER_URL_PROP;
 import static com.linkedin.venice.vpj.VenicePushJobConstants.VENICE_STORE_NAME_PROP;
 
-import com.google.common.annotations.VisibleForTesting;
 import com.linkedin.avroutil1.compatibility.AvroCompatibilityHelper;
 import com.linkedin.d2.balancer.D2Client;
 import com.linkedin.venice.PushJobCheckpoints;