Change GitLab to smth better.

GitLab is "Open Core".. The CE (Community Edition) is MIT-licensed..[1] GitLab is not LibreJS-compliant.[2]

I think Trisquel should leave it for smth better. For example: Savane[3], Forgejo[4], Sourcehut[5].

[1] https://en.wikipedia.org/wiki/GitLab
[2] https://www.gnu.org/software/repo-criteria-evaluation.html
[3] https://directory.fsf.org/wiki/Savane
[4] https://forgejo.org/
[5] https://directory.fsf.org/wiki/Sourcehut