Remove "gitlab-shell"-Redis from the diagram

"gitlab-shell"-Redis relationship in the component diagram at GitLab
Architecture Overview does not exist anymore.

See https://gitlab.com/gitlab-org/gitlab-shell/-/merge_requests/181

doc/development/architecture.md

@@ -53,7 +53,6 @@ graph TB
 
   GitLabShell --TCP 8080 -->Unicorn["Unicorn (GitLab Rails)"]
   GitLabShell --> Praefect
-  GitLabShell --> Redis
   Unicorn --> PgBouncer[PgBouncer]
   Unicorn --> Redis
   Unicorn --> Praefect