Merge branch 'gitlab-agent' into 'master'

Update the intro for GitLab agent

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/139522



Merged-by: Lorena Ciutacu <lciutacu@gitlab.com>
Approved-by: Lorena Ciutacu <lciutacu@gitlab.com>
Co-authored-by: Ashraf Khamis <akhamis@gitlab.com>