[Cleanup] Clean up the xmpp remainder (#4286)

* [Web] Update russian translation (lang.ru.json)

* XMPP cleanup

Co-authored-by: Dmitriy Alekseev <1865999+dragoangel@users.noreply.github.com>

helper-scripts/docker-compose.override.yml.d/EXTERNAL_DNS/docker-compose.override.yml

@@ -42,7 +42,3 @@ services:
     dockerapi-mailcow:
       dns:
         - my.resolvers.ip.addr
-
-    ejabberd-mailcow:
-      dns:
-        - my.resolvers.ip.addr