Run git pull after changing to a given revision

What does this MR do and why?

I noticed in: https://gitlab.com/sylva-projects/sylva-core/-/jobs/6265299953 (scheduled pipeline to test upgrade from 1.0.0 to main) that we have an issue when checking out main branch during the update.

Changing git revision to use main
Previous HEAD position was a295c226 Merge branch 'stricter-monitoring-schema' into 'main'
Switched to branch 'main'
Your branch is behind 'origin/main' by 272 commits, and can be fast-forwarded.
  (use "git pull" to update your local branch)
Current revision: 9d4858729b20ac16210454ae7f29b887e1e35b5a

As the default GIT_STRATEGY is fetch we reuse the current git repo present on the runner (if we stay on the same runner) so the main branch is potentially far behind of what we expect.

We could switch the GIT_STRATEGY to clone but it will be slower for all others jobs. So this MR propose to just force the pull after the checkout to be sure we are up to date with origin/main

Related reference(s)

Test coverage