Resolves#10102
Adjust the SSH key verification instructions for Windows CMD to make it work.
## Test
1. Use Windows.
2. Go to the user settings.
3. Go to "SSH / GPG keys"
4. Add a SSH key.
5. Click on the "Verify" button for the SSH key.
6. Use the Windows CMD command to verify.
7. Verify that this generates a signature that is accepted by Forgejo.
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/10106
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Melissa Geels <melissa@nimble.tools>
Co-committed-by: Melissa Geels <melissa@nimble.tools>
