TYP: remove ignore from pandas/tseries/frequencies.py
Related to #37715
mypy ignore[assignment] was removed from pandas/tseries/frequencies.py
@twoertwein, could you please take a look at my last changes? Looks like there are no failures in ci, but the last check `Doc Build and Upload` is still in progress for about 6 hours. @natmokval can you merge main > @natmokval can you merge main

@jbrockmendel, I can merge main but these changes are in main already (see pr #53120). So I think it's better to close this pr. Sorry, I had to do it earlier.