Merge branch...

Merge branch '22352-cannot-install-gitlab-shell-on-ubuntu-server-with-no-previous-gitlab-install' into 'master'

Correct gitlab-shell installation instructions in docs

## Why was this MR needed?

With the introduction of repository storages validations it becomes necessary to add the flag `SKIP_STORAGE_VALIDATION` to the gitlab-shell install command, since that command will create the storage paths

## What are the relevant issue numbers?

Closes #22352

[ci skip]

See merge request !6579

doc/install/installation.md

@@ -381,7 +381,7 @@ sudo usermod -aG redis git
 GitLab Shell is an SSH access and repository management software developed specially for GitLab.
 
     # Run the installation task for gitlab-shell (replace `REDIS_URL` if needed):
-    sudo -u git -H bundle exec rake gitlab:shell:install REDIS_URL=unix:/var/run/redis/redis.sock RAILS_ENV=production
+    sudo -u git -H bundle exec rake gitlab:shell:install REDIS_URL=unix:/var/run/redis/redis.sock RAILS_ENV=production SKIP_STORAGE_VALIDATION=true
 
     # By default, the gitlab-shell config is generated from your main GitLab config.
     # You can review (and modify) the gitlab-shell config as follows: