Resolve "rake gitlab:shell:install creates ~git/.ssh/environment which gitlab:check complains about"

What does this MR do?

Stops the gitlab:shell:install task from creating ~git/.ssh/environemnet

Are there points in the code the reviewer needs to double check?

If there was a good reason why this file was created in the first place, then the fix may be instead to fix the gitlab:check rake task so that it tolerates the presence of the file.

Why was this MR needed?

All installs from source currently fail.

Screenshots (if relevant)

N/A

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• [N/A] API support added
• Tests added for this feature/bug (existing tests were failing)
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

Closes #38540 (closed)