Handle numbered weekday (MO(-1)) with frequencies higher than monthly by dropping the number.
Handle numbered weekday (MO(-1)) with frequencies higher than monthly
by dropping the number.

pganssle/dateutil-test-codecov,pganssle/dateutil-test-codecov,abalkin/dateutil,mjschultz/dateutil,adamgreig/python-dateutil,emsoftware/python-dateutil,sprymix/python-dateutil,jenshnielsen/dateutil,abalkin/dateutil,Bachmann1234/dateutil,sprymix/dateutil