Remove expired ports:

2020-10-25 converters/zbase32: does not build with python3
2020-10-25 devel/py-PEAK-Rules: does not build with python3
2020-10-25 editors/nvi-devel: Unsupported upstream since 2015, please switch to editors/nvi2

See https://people.freebsd.org/~rene/stuff/old-ports.txt for "unremoveable" ports.