Symlink the CE HTML files on production and review apps

Now that we have a single codebase, the CE and EE docs are identical, thus duplicate. This leads to having almost twice the size of artifacts, which can cause Pages errors.

With this change, we remove the CE HTML content and use a symlink to EE instead. The structure will remain the same without the duplicate content.

You can see how much size we save in this job where I calculated before/after with du -sh https://gitlab.com/gitlab-org/gitlab-docs/-/jobs/277261201:

$ du -sh public
382M	public
$ rm -r public/ce
$ ln -s ee public/ce
$ du -sh public
198M	public

Resolves #418 (closed)

Limitation

FYI, with the hack I crafted to buy us some space, when you visit https://docs.gitlab.com/ce/, the left navbar would still point to /ee/. That's a limitation of the symlink I applied, but I thought we could live with that.