Documentation for my changes to ssh commit signing in <https://github.com/go-gitea/gitea/pull/34341>.
* Renames "GPG Commit Signatures" to "GPG/SSH Commit Signatures", since the url is called just signing and creating a new page would duplicate a lot
* _"The default option and repository specific signing keys are not supported for ssh keys"_
* the original draft implementation did support this for ssh keys
* this warning should avoid people expecting this gitconfig style things to work for ssh keys, since verifying is disabled in this case (e.g. pre 1.25 undocumented behavior preserved).
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-on: https://gitea.com/gitea/docs/pulls/241
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Christopher Homberger <christopher.homberger@web.de>
Co-committed-by: Christopher Homberger <christopher.homberger@web.de>
