Pass the destination File to the callback

The current argument is unused and it should have been removed
with commit 81229329f1
("Generate download clients using a builder class"). Instead of
removing it completely, use it to pass the File of the download.

src/org/lineageos/updater/UpdatesActivity.java

@@ -241,7 +241,7 @@ public class UpdatesActivity extends AppCompatActivity {
             }
 
             @Override
-            public void onSuccess(String response) {
+            public void onSuccess(File destination) {
                 runOnUiThread(new Runnable() {
                     @Override
                     public void run() {