Azure on Windows does not use `setup_conda_environment.cmd`

[gmarkall]

Identified in #922. Instead of running setup_conda_environment.cmd to set up the environment, it runs commands inside azure-windows.yml. It seems that this was originally due to some issues with calling setup_conda_environment.cmd, mentioned in https://github.com/numba/llvmlite/commit/276d2023bb2dc215f75a976b631bb88013c2c427#r239559309, but these should be worked out so that the setup of the conda environment is unified between the Azure Windows build and other environments.

[sklam]

In the case that we are not going to fix it soon, i'd suggest deleting setup_conda_environment.cmd to avoid confusion