devel/py-rq: Update to 2.0.0

• Remove no-op PY_DEPENDS while I'm here.

• Add CONFLICTS_INSTALL entry which is needed due the newly created port devel/py-rq1.

Changelog:

https://github.com/rq/rq/releases/tag/v2.0

PR: 282649
Approved by: skreuzer (maintainer)
MFH: No (contains breaking changes)