Add 'second-class citizen' as a Misused Term in Communications Handbook

Why is this change being made?

Add 'second-class citizen' as a Misused Term in Communications Handbook

For context, this is often used to describe the feeling of a remote team member which is not seen or treated equally within a hybrid-remote environment (e.g. not GitLab, which is all-remote). https://about.gitlab.com/company/culture/all-remote/hybrid-remote/#disadvantages-to-hybrid-remote

Related merge requests to update terminology

1. !51890 (merged)
2. !51915 (merged)

This MR also cleans up URL formatting, swapping absolute URLs with relative URLs, per the GitLab Style Guide.

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
• Assign this change to the correct DRI
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to your manager.
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies.
  • If the changes relate to any part of the project other than updates to content and/or data files please make sure to ping @gl-static-site-editor in a comment for a review and merge. For example changes to .gitlab-ci.yml, JavaScript/CSS/Ruby code or the layout files.

For help with failing pipelines reach out in #mr-buddies in Slack