Specify fetch-depth during mirroring to gitlab.

[rosiel]

GitHub Issue: actions failed, e.g. https://github.com/Islandora/islandora/actions/runs/6300409377/job/17103202042#step:4:20

Similar ticket, taking the --force option:

• Force push 2x branch to Gitlab #981

• Issue with the mirroring script/source for this fix: Run with actions/checkout@v3 SvanBoxel/gitlab-mirror-and-ci-action#17

What does this Pull Request do?

We were having problems because the during the action, the checked out repository didn't match the target gitlab -

hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again. 

There dont' seem to be commits in gitlab that aren't in github.

So, this is probably due to the new checkout actions including v3 defaulting to only check out information about the latest commit. We apparently can use fetch-depth: 0 to revert to getting all commits.

@aOelschlager , @Islandora/committers

[aOelschlager]

This makes sense.