Add Doc Crosslink from Admin to Project Settings

In the admin guide, there was a reference to disabling a container
registry on a per-project basis. This has been updated to cross-link to
the user guide - specifically to the relevant section.
Signed-off-by: Raimund Hook <raimund.hook@exfo.com>

doc/administration/packages/container_registry.md

@@ -617,8 +617,7 @@ In the examples below we set the Registry's port to `5001`.
 ## Disable Container Registry per project
 
 If Registry is enabled in your GitLab instance, but you don't need it for your
-project, you can disable it from your project's settings. Read the user guide
-on how to achieve that.
+project, you can [disable it from your project's settings](../../user/project/settings/index.md#sharing-and-permissions). 
 
 ## Use an external container registry with GitLab as an auth endpoint