Switch from github.com/xanzy/go-gitlab to gitlab.com/gitlab-org/api/client-go

github.com/xanzy/go-gitlab is since 0.115.0 officially deprecated. The project has been archived on github and migrated to gitlab.

This migration will be straightforward:

• To continue using the package, simply update your import path and go.mod reference from github.com/xanzy/go-gitlab to gitlab.com/gitlab-org/api/client-go.
• No other breaking changes are expected.

mentioned in commit a1403387

mentioned in merge request !98 (merged)

mentioned in commit d3c110b6

closed with commit a1403387