Change gitlab.rc to code.rc to support upcoming domain name change

[wwarriner]

Pull Request

Intent

We are changing the on-premises GitLab domain and must reflect the change in the docs.

Proposed Changes

• Change gitlab.rc.uab.edu to code.rc.uab.edu wherever it occurs.
• Make style and SPAG updates where needed.

Changes to Section Headers

N/A

Changes to Page URLs

N/A

Related or Fixed Issues

Fixes #1034

Accessibility Checklist

I have ensured all of the following for new or changed content:

• all images have appropriate alt text. Guidelines
• all images with text have sufficient contrast ratio. Checker
• all image text is transcribed or described in body text.
• all technical terms, jargon, and abbreviations are introduced before they are used.

Style Checklist

I have done all of the following:

• searched for other relevant pages and crosslinked from my content to them.
• searched for other relevant pages and crosslinked from them to my content.
• added redirects in mkdocs.yml for any moved headers or pages.
• defined new technical terms, jargon, and abbreviations in the glossary.
• searched for existing technical terms, jargon, and abbreviations in the glossary and added crosslinks to them.
• properly formatted and introduced key branding terms. List here.

[bdu-birhanu]

Looks good to me.