Remove expired ports:
2020-09-01 multimedia/w_scan: No longer developed since September 2017, MASTER_SITES gone
2020-08-31 net/ntp-devel: Current devel branch of ntp is no longer published
2020-08-31 mail/postfix-policyd-spf-python: Use mail/py-spf-engine instead (Project is superseded by successor)
2020-08-26 graphics/py-pyembree: Broken for more than 6 months
2020-08-26 games/asteroid: Broken for more than 6 months