Merge branch 'update-sidekiq-processes-docs' into 'master'

Rewrite Sidekiq processes docs

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/103228



Merged-by: Achilleas Pipinellis <axil@gitlab.com>
Approved-by: Achilleas Pipinellis <axil@gitlab.com>
Co-authored-by: Sean McGivern <sean@gitlab.com>