postfix: Use Debian Bullseye's config as standard

Signed-off-by: Maximilian Wilhelm <max@sdn.clinic>

postfix/init.sls

@@ -23,6 +23,7 @@ postfix:
     - source:
       - salt://postfix/master.cf.H_{{ grains['id'] }}
       - salt://postfix/master.cf.{{ grains.os }}.{{ grains.oscodename }}
+      - salt://postfix/master.cf
     - watch_in:
       - service: postfix