🌱 migrate gitlab client import

[spencerschrock]

What kind of change does this PR introduce?

dep update

• PR title follows the guidelines defined in our pull request documentation

What is the current behavior?

We used the github.com/xanzy/go-gitlab package.

What is the new behavior (if this is a feature change)?**

The package is deprecated, in favor of the GitLab ran one:
https://gitlab.com/gitlab-org/api/client-go

• Tests for the changes have been added (for bug fixes/features)

Which issue(s) this PR fixes

Related to #4451

Special notes for your reviewer

Does this PR introduce a user-facing change?

For user-facing changes, please add a concise, human-readable release note to
the release-note

(In particular, describe what changes users might need to make in their
application as a result of this pull request.)

NONE

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.63%. Comparing base (353ed60) to head (0d1aefb).
Report is 79 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4452      +/-   ##
==========================================
+ Coverage   66.80%   68.63%   +1.82%     
==========================================
  Files         230      242      +12     
  Lines       16602    18031    +1429     
==========================================
+ Hits        11091    12375    +1284     
- Misses       4808     4848      +40     
- Partials      703      808     +105