pgp: don't assume protocol/micalg ordering in doctest output.

pgp: don't assume protocol/micalg ordering in doctest output.

The Content-Type header is eventually set by Message.add_header(),
which gets extra parameters from **_params and iterates over them with
_params.items().  _params is a dict, so .items() is not sorted.  I
forced the ordering in the pgp-mime doctests, so here I assume the
micalg field is correct and just use ELLIPSIS.