www/py-caldav: Update to 0.9.0

https://github.com/python-caldav/caldav/releases

While here

• set the version specifications for RUN_DEPENDS to match any version, since upstream does not make any requirements
• Enable tests.

Reviewed by: koobs
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D35226