Remove connection between GitLab Shell and Redis from updated GitLab basic architecture diagrams (14.8)

As gitlab-shell!181 (merged) removed connection between GitLab Shell and Redis since 2018, !80083 (merged) (by @sunjungp) should be updated as so.

This was easily found due to https://nicolasdular.gitlab.io/gitlab-polish-gallery/?milestone=14.8, thanks @nicolasdular for building it.

Part of #229893 (closed)

As-is diagram

https://gitlab.com/gitlab-org/gitlab/-/blob/3499a2260eb0fc646b7031b3da53533c8cdefead/doc/development/img/architecture_simplified.png

Proposed diagram

https://miro.com/app/board/uXjVOH3lzXo=/?invite_link_id=813644894399

exported JPEG