Resend webxdc sent by another user [to fix group that became plaintext on 2.46]

[anedroid]

Even resending sometimes doesn’t work:

1. There are decryption errors on the receiver’s side.
2. Receiver updates the client.
3. After updating, the previous messages doesn’t get decrypted, but the new ones.
4. Resending doesn’t work - either for it uses the same encryption key which the receiver have not, or because the sender only resends to new group members.

…which is especially problematic for XDC apps and their updates.