[mailman/certbot] Certbot is already generating a wildcard certificate

Signed-off-by: Yohann D'ANELLO <ynerant@crans.org>

group_vars/mailman.yml

 ---
-loc_certbot:
-  - dns_rfc2136_server: '172.16.10.147'
-    dns_rfc2136_name: certbot_challenge.
-    dns_rfc2136_secret: "{{ vault.certbot_dns_secret }}"
-    mail: root@crans.org
-    certname: crans.org
-    domains: "*.crans.org"
-
 loc_nginx:
   service_name: mailman3
   upstreams: