[Postfix] Add watchdog@localhost alias

data/Dockerfiles/postfix/postfix.sh

@@ -13,6 +13,7 @@ done
 cat <<EOF > /etc/aliases
 # Autogenerated by mailcow
 null: /dev/null
+watchdog: /dev/null
 ham: "|/usr/local/bin/rspamd-pipe-ham"
 spam: "|/usr/local/bin/rspamd-pipe-spam"
 EOF