Docs: Cross-link mentions with related settings

doc/user/discussions/index.md

@@ -47,6 +47,8 @@ in a different color.
 
 Avoid mentioning `@all` in issues and merge requests, because it sends an email notification
 to all the members of that project's group. This might be interpreted as spam.
+Notifications and mentions can be disabled in
+[a group's settings](../group/index.md#disable-email-notifications).
 
 ## Add a comment to a merge request diff
 

doc/user/group/index.md

@@ -717,7 +717,8 @@ To disable email notifications:
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/21301) in GitLab 12.6.
 
 You can prevent users from being added to a conversation and getting notified when
-anyone mentions a group in which those users are members.
+anyone [mentions a group](../discussions/index.md#mentions)
+in which those users are members.
 
 Groups with disabled mentions are visualized accordingly in the autocompletion dropdown list.