chore: remove deprecated Mail service

examples/plausible/docker-compose.yml

@@ -1,9 +1,5 @@
 version: "3.3"
 services:
-  #mail:
-  #  image: bytemark/smtp
-  #  restart: always
-  #  container_name: plausible-smtp
 
   plausible_db:
     image: postgres:16-alpine