Add gitlab_shell. authorized_keys_file to gitlab.yml

What does this MR do?

This adds gitlab_shell.authorized_keys_file setting to gitlab.yml.

gitlab-rails recipe has been configured to set it based on the node['gitlab']['gitlab-shell']['auth_file'].

This is a step to migrate that setting to gitlab-rails as it won't be needed by gitlab-shell anymore later on.

Checklist

See Definition of done.

• Change added to CHANGELOG.md. Not applicable for Documentation changes and minor changes.
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA, if applicable
• MR targeting master branch
• MR has a green pipeline on GitLab.com

Reviewer Checklist

In addition to above, reviewer must:

• Pipeline is green on dev.gitlab.org if the change is not touching documentation or internal cookbooks

References

Issue: #4185 (closed)

GitLab CE MR: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/25598#note_147323288

Closes #4185 (closed)