Merge branch 'ajwalker/script-timeout-docs' into 'master'

Add documentation for script/after_script timeout variables

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/131785



Merged-by: Fiona Neill <fneill@gitlab.com>
Approved-by: Axel von Bertoldi <avonbertoldi@gitlab.com>
Reviewed-by: Fiona Neill <fneill@gitlab.com>
Reviewed-by: Axel von Bertoldi <avonbertoldi@gitlab.com>
Co-authored-by: Arran Walker <ajwalker@gitlab.com>