[GitLab implementation] Disable Git button if using external repo

We use an external GitLab repository with our P.sh projects. So, none of the buttons (git, branch, merge or sync) except one (snapshot) is useful to us in the project dashboard.

Once there's an external repo implementation, the project dashboard should hide these buttons, or make them readonly. Since an accidental use of these would potentially harm the GitLab integration, and/or what's been deployed.