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