Remove obsolete GitLab OAuth settings

I went through all the settings for doc!108 (merged) and found that we still had the gitlab settings, even though they are no longer used since !2210 (merged). That MR had removed the Django settings but not the YAML config options.

changed milestone to %Arkindex 1.6.1

requested review from @babadie

assigned to @erouchet

added 3 commits

• 58f00c24...6652b69d - 2 commits from branch master
• 6cc9ec21 - Remove obsolete GitLab OAuth settings

Compare with previous version

added 3 commits

• 6cc9ec21...50351959 - 2 commits from branch master
• 7bf36bb2 - Remove obsolete GitLab OAuth settings

Compare with previous version

enabled an automatic merge when the pipeline for 7bf36bb2 succeeds

merged