chore: Annotate overridden function

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

app/src/main/java/com/owncloud/android/ui/fragment/GalleryFragment.java

@@ -195,6 +195,7 @@ public class GalleryFragment extends OCFileListFragment implements GalleryFragme
         showAllGalleryItems();
     }
 
+    @Override
     public int getColumnsCount() {
         return columnSize;
     }