Merge branch 'gy-handle-sidekiq-concurrency-deprecation-ra-docs' into 'master'

Handle Sidekiq concurrency config deprecation in Ref Arch docs

Closes gitlab-org/quality/reference-architectures#285

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/144191



Merged-by: Achilleas Pipinellis <axil@gitlab.com>
Co-authored-by: Grant Young <gyoung@gitlab.com>