Remove unnecessary TODO

Exception handlers are executed in the context of a mailbox instance and already have access to the inbound email.

lib/action_mailbox/base.rb

@@ -27,7 +27,6 @@ class ActionMailbox::Base
       end
     end
   rescue => exception
-    # TODO: Include a reference to the inbound_email in the exception raised so error handling becomes easier
     rescue_with_handler(exception) || raise
   end