DEPS: Bump minimum Numba version

[mroeschke]

xref #43172 (comment)

The current min version is 0.46.0 which came out 2019-10-10.

Bumping to at least 0.49.0 (which came out 2020-04-17) would allow this version check to be removed:

pandas/pandas/core/util/numba_.py

Line 90 in b9e90dc

if Version(numba.__version__) >= Version("0.49.0"):

[fangchenli]

I bumped the min support version to 0.50.1 in #41989. So only need to clean up the compat.

[mroeschke]

Ah thanks. I'll close and just update the tests & compat.