This reverts commit 2411e72a.

Mirror branches from gitlab

Pull requests are now to be opened as merge requests in GitLab.

CI has moved from Travis to GitHub action and from GitHub action to
GitLab CI. This file hasn't been used in several years.

This breaks in some cases, so just use function parameters instead.

Call sphinx-build in a similar way as lisa-doc-build so that old
branches build correctly.

We don't have a 23.04 runner

Use Ubuntu 23.04 for a version of pandoc that is supported by Sphinx.

FIX