remove the unused import

Author: rockspore

google-cloud-storage/src/main/java/com/google/cloud/storage/GrpcStorageOptions.java

@@ -50,7 +50,6 @@
 import com.google.api.gax.tracing.ApiTracerFactory;
 import com.google.api.pathtemplate.PathTemplate;
 import com.google.auth.Credentials;
-import com.google.auth.oauth2.ComputeEngineCredentials;
 import com.google.cloud.NoCredentials;
 import com.google.cloud.ServiceFactory;
 import com.google.cloud.ServiceOptions;