Fix import order in auth sample. (#1080)

Author: dzlier-gcp

auth/src/main/java/com/google/cloud/auth/samples/AuthExample.java

@@ -17,8 +17,8 @@
 package com.google.cloud.auth.samples;
 
 import com.google.api.gax.paging.Page;
-import com.google.auth.oauth2.ComputeEngineCredentials;
 import com.google.auth.appengine.AppEngineCredentials;
+import com.google.auth.oauth2.ComputeEngineCredentials;
 import com.google.auth.oauth2.GoogleCredentials;
 import com.google.cloud.storage.Bucket;
 import com.google.cloud.storage.Storage;