Fix minor error in doc/security/user_email_confirmation.md

Originally submitted at
https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3190.
Signed-off-by: Rémy Coutable <remy@rymai.me>

doc/security/user_email_confirmation.md

@@ -4,4 +4,4 @@ Gitlab admin can enable email confirmation on sign-up, if you want to confirm al
 user emails before they are able to sign-in.
 
 In the Admin area under **Settings** (`/admin/application_settings`), go to section
-**Sign-in Restrictions** and look for **Send confirmation email on sign-up** option.
+**Sign-up Restrictions** and look for **Send confirmation email on sign-up** option.