PST importer: fix name of MIME multipart/alternative
As reported and found on the HTML email problem[1] thread, the pst importer wrongly sets the Content-Type to multipart/alternate instead of the right name multipart/alternative (RFC 2046), which leads to such emails not being properly shown on evolution.
1- https://mail.gnome.org/archives/evolution-list/2020-January/msg00003.html