Whitelist authorized_keys.lock in the gitlab:check rake task

What does this MR do?

Adds a missed file to the whitelist for the git_user_default_ssh_config check introduced in %10.0

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

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Review
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #38635 (closed)