Remove unused import

src/com/owncloud/android/ui/activity/FileDisplayActivity.java

@@ -46,7 +46,6 @@ import android.preference.PreferenceManager;
 import android.provider.OpenableColumns;
 import android.support.design.widget.Snackbar;
 import android.support.v4.app.Fragment;
-import android.support.v4.app.FragmentManager;
 import android.support.v4.app.FragmentTransaction;
 import android.support.v4.content.ContextCompat;
 import android.support.v4.view.GravityCompat;