static type checks fail since numpy 1.20

[wyli]

the recent numpy update (https://github.com/numpy/numpy/releases/tag/v1.20.0) breaks the pull request's type checks https://github.com/Project-MONAI/MONAI/pull/1532/checks?check_run_id=1807350179#step:7:284

[Nic-Ma]

Hi @wyli ,

Maybe let fix the numpy version?
I don't see any feature requirements for a newer numpy so far.

Thanks.

[wyli]

many of the errors are actually valid points, I'll create a PR on those first