Remove invalid entrypoint: luigi.tools.migrate (#2257)
Remove invalid entrypoint: luigi.tools.migrate (#2257)

Fixes https://github.com/spotify/luigi/issues/2256

File was made obsolete by: 66ff3c5f8259f62f4540097629b7600834bb5b29
jamesmcm/luigi,soxofaan/luigi,edx/luigi,Houzz/luigi,jamesmcm/luigi,samuell/luigi,edx/luigi,foursquare/luigi,soxofaan/luigi,rayrrr/luigi,dlstadther/luigi,edx/luigi,spotify/luigi,PeteW/luigi,adaitche/luigi,spotify/luigi,samuell/luigi,riga/luigi,dlstadther/luigi,riga/luigi,dlstadther/luigi,edx/luigi,rayrrr/luigi,riga/luigi,soxofaan/luigi,foursquare/luigi,Magnetic/luigi,PeteW/luigi,rayrrr/luigi,jamesmcm/luigi,rayrrr/luigi,adaitche/luigi,riga/luigi,jamesmcm/luigi,Houzz/luigi,foursquare/luigi,Houzz/luigi,samuell/luigi,spotify/luigi,adaitche/luigi,samuell/luigi,PeteW/luigi,PeteW/luigi,Houzz/luigi,foursquare/luigi,Magnetic/luigi,spotify/luigi,Magnetic/luigi,Magnetic/luigi,adaitche/luigi,dlstadther/luigi,soxofaan/luigi