Fix format

Author: rlazo

firebase-messaging/src/test/java/com/google/firebase/messaging/shadows/ShadowMessenger.java

@@ -21,7 +21,6 @@
 import org.robolectric.annotation.Implementation;
 import org.robolectric.annotation.Implements;
 import org.robolectric.annotation.RealObject;
-import org.robolectric.shadow.api.Shadow;
 import org.robolectric.util.reflector.Direct;
 import org.robolectric.util.reflector.ForType;