Add comment about tls for ldap method

`omniauth-ldap` also supports tls for ldap method

config/gitlab.yml.example

@@ -124,7 +124,7 @@ production: &base
     base: '_the_base_where_you_search_for_users'
     port: 636
     uid: 'sAMAccountName'
-    method: 'ssl' # "ssl" or "plain"
+    method: 'ssl' # "tls" or "ssl" or "plain"
     bind_dn: '_the_full_dn_of_the_user_you_will_bind_with'
     password: '_the_password_of_the_bind_user'
     allow_username_or_email_login: true