postfix: Remove special "fast-path" smtpd + Remove unneeded smtpd service that was used by SpamAssassin
With the switch to Rspamd from SpamAssassin it isn't faster anymore, because Rspamd is configured as a global milter where SA was configured as a smtpd_proxy_filter/content_filter for smtp/submission.
This only requires changes to Flyspray AFAIK (change smtp_server
in the flyspray_prefs
table).