Remove some expired ports:

2020-12-31 emulators/fceux: Uses Python 2.7 version of scons, and Python 2.7 which is EOLed upstream
2020-12-31 emulators/gem5: Uses Python 2.7 version of scons, and Python 2.7 which is EOLed upstream
2020-12-31 emulators/nonpareil: Uses Python 2.7 version of scons, and Python 2.7 which is EOLed upstream
2020-12-31 games/freera: Uses Python 2.7 version of scons, and Python 2.7 which is EOLed upstream
2020-12-31 games/glob2: Uses Python 2.7 version of scons, and Python 2.7 which is EOLed upstream
2020-12-31 games/marsnomercy: Uses Python 2.7 version of scons, and Python 2.7 which is EOLed upstream
2020-12-31 games/netpanzer: Uses Python 2.7 version of scons, and Python 2.7 which is EOLed upstream
2020-12-31 games/pingus: Uses Python 2.7 version of scons, and Python 2.7 which is EOLed upstream
2020-12-31 graphics/goxel: Uses Python 2.7 version of scons, and Python 2.7 which is EOLed upstream
2020-12-31 graphics/sk1libs: Uses Python 2.7 which is EOLed upstream
2020-12-31 graphics/uniconvertor: Uses deprecated version of python