Overloaded signatures aren't rendered in HTML docs

[stevepiercy]

I don't see the overloaded signature in https://icalendar--1130.org.readthedocs.build/en/1130/reference/api/icalendar.cal.calendar.html#icalendar.cal.calendar.Calendar.from_ical.

Possibly related issue tox-dev/sphinx-autodoc-typehints#529.

Originally posted by @stevepiercy in #1129

[niccokunzmann]

This is also true for Component.from_ical