`M-x vimgolf-revert` from the completion screen doesn't restart the challenge properly.

[timvisher]

Steps to reproduce:

1. Solve a challenge in some way
2. Submit the challenge
3. C-c C-v r or M-x vimgolf-revert
4. Solve the challenge in another way
5. Submit the challenge again

Expected Results:

• Update the success screen with the new keystrokes.
• Display the correct keystroke count in the minibuffer.

Actual Results:

• The success screen is not updated (still has the original submission)
• The minibuffer displays something like Hurray! You solved 55b18bbea9c2c30d04000001 in 0 keystrokes!

Notes:

If you revert the challenge and then activate the diff function (C-c C-v d) and then continue the challenge it works as expected.