fix: remove a few leftover fast server artifacts

Procfile.options

@@ -4,8 +4,6 @@ pid_root: /tmp/postal/pids
 processes:
   web:
     restart_mode: usr1
-  fast:
-    restart_mode: term-start
   smtp:
     restart_mode: usr1
   worker:

lib/postal.rb

@@ -13,7 +13,6 @@ module Postal
     autoload :HTTP
     autoload :HTTPSender
     autoload :Job
-    autoload :LetsEncrypt
     autoload :MessageDB
     autoload :MessageInspection
     autoload :MessageParser

script/update_process_concurrency.rb

@@ -8,9 +8,6 @@ hash = {
   'processes' => {
     'worker' => {
       'quantity' => worker_quantity
-    },
-    'fast' => {
-      'quantity' => Postal.config.fast_server.enabled? ? 1 : 0
     }
   }
 }.to_yaml