Revert "nagios / external: make mail_queue internal only"

This reverts commit 84f03db63c.

roles/nagios_server/tasks/main.yml

@@ -228,7 +228,6 @@
     - dns.cfg
     - haproxy.cfg
     - memcached.cfg
-    - mail_queue.cfg
     - nagios.cfg
     - pagure_redis.cfg
     - ping.cfg
@@ -399,6 +398,7 @@
   ansible.builtin.template: src=nagios/services/{{item}}.j2 dest=/etc/nagios/services/{{item}} mode=0644 owner=root group=root
   with_items:
     - websites.cfg
+    - mail_queue.cfg
   when: env == "production"
   tags:
   - nagios_server