ui:preview: Removed unused @Override method so that we simply inherit it.

Overriding a method just to call the same method from the super class without performing any other actions is useless and misleading.

src/main/java/com/owncloud/android/ui/preview/PreviewImageFragment.java

@@ -476,11 +476,6 @@ public class PreviewImageFragment extends FileFragment {
         }
     }
 
-    @Override
-    public void onPause() {
-        super.onPause();
-    }
-
     @SuppressFBWarnings("Dm")
     @Override
     public void onDestroy() {