Fixes `Plug.Conn.NotSentError` that causes a 5xx error in response
instead of 404 and 400.
Fixes pattern matching error caused by different response format
in test and non-test env: `Pleroma.Emails.Mailer.deliver_async` returns
:ok when PleromaJobQueue is enabled and `{:ok, _}` when it's disabled.
In tests, it's disabled.