MAINT: set `zip_safe` to `False` in `setup.py`

[person142]

Closes https://github.com/numpy/numpy-stubs/issues/36.

See the mypy docs:

https://mypy.readthedocs.io/en/latest/installed_packages.html#making-pep-561-compatible-packages

for more information.

[person142]

Since this is a small change, I will merge it tomorrow unless someone complains.

[rgommers]

Merged, thanks Josh