TYP: Upgrade to mypy 0.920
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them

new mypy was released

Converting to draft till mypy is on conda-forge > Converting to draft till mypy is on conda-forge

seems to be available: https://anaconda.org/conda-forge/mypy yep, ci is green, was failing before one more rebase if you don't mind (as just merged your typing PR) rebased and greenish @jreback thanks @phofl 