Move repo links from gitlab to github

There are still a number of links pointing towards the gitlab repository mirror instead of the upstream github. Here is one example:

https://github.com/acts-project/acts-project.github.io/blob/b0b395b6a03e2641ecfff60e07f474c510bba5f4/mkdocs.yml#L15-L20

This is the most notable issue (apologies for MS paint skills):


A quick grep shows 33 gitlab links. Should these going to be updated to the new upstream or are they intentionally kept on gitlab?