Remove ill-placed `connect` assert
Remove ill-placed `connect` assert

the `connect` method is only called in the `SMTP()`-constructor, and
not in the `send_mail` method.  The constructor is never executed
because the whole SMTP class is mocked, so testing for a `connect()`
call is pointless.

agdsn/sipa,agdsn/sipa,agdsn/sipa,agdsn/sipa