Merge branch 'mg-update-sidekiq-max-concurrency-default-docs' into 'master'

Update default Sidekiq max_concurrency doc

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/112147



Merged-by: Felipe Artur <fcardozo@gitlab.com>
Approved-by: Achilleas Pipinellis <axil@gitlab.com>
Approved-by: Felipe Artur <fcardozo@gitlab.com>
Co-authored-by: Gregorius Marco <gmarco@gitlab.com>