Refactor: Remove overridden onBackPressed()

- onDestroy() already handles cancelling async tasks

app/src/main/java/org/kiwix/kiwixmobile/zim_manager/local_file_transfer/LocalFileTransferActivity.java

@@ -583,9 +583,4 @@ public class LocalFileTransferActivity extends AppCompatActivity implements
     super.onDestroy();
     cancelAsyncTasks();
   }
-
-  @Override
-  public void onBackPressed() {
-    wifiDirectManager.closeLocalFileTransferActivity();
-  }
 }

app/src/main/java/org/kiwix/kiwixmobile/zim_manager/local_file_transfer/WifiDirectManager.java

@@ -212,6 +212,7 @@ public class WifiDirectManager implements WifiP2pManager.ChannelListener, WifiP2
     });
   }
 
+  // TODO: Shift async tasks to WDM and handle cleanup from here itself
   public void closeLocalFileTransferActivity() {
     activity.cancelAsyncTasks();