Remove expired ports:

2021-02-14 www/rtv: Abandoned, use www/py-ttrv or www/py-tuir instead
2021-02-15 textproc/py-sphinxcontrib-websupport11: Use textproc/py-sphinxcontrib-websupport instead
2021-02-15 textproc/py-sphinx18: Old version, use textproc/py-sphinx instead