Scrub wiki git installation instructions in favor of git-with-openssh

[oznogon]

The advice in #2392, #1449, #1260, and #893 to use git-with-openssh contradicts the wiki, which advises using git and openssh in three articles:

• Github with SSH key
• Example Setup Scripts
• Theming Powershell

No wiki article mentions git-with-openssh, so there is no explanation of what it is or what distinguishes it from git and openssh. The notes when installing git and openssh still suggest setting GIT_SSH when they should probably suggest using git-with-openssh if that's the intent. Buckets in general don't have their own documentation to consult.

At least until #2414 is resolved, the wiki and bucket notes for git and openssh should be updated to instead suggest git-with-openssh for the purpose of using git with ssh.