Updates to env

[jdebacker]

This PR tries to fix failing tests by:

1. Removing multiprocessing from environment.yml (this package is in the standard library)
2. Fixing a parentheses in test_cli.py

Also, prior work on this branch had commented out a function that used pandoc due to some local issues with the package. This PR brings back that function.

[jdebacker]

@andersonfrailey Note that I'm leaving OG-USA out of the environment.yml because (1) it's not on conda-forge and so would cause issues building the taxbrain package there and (2) I need to figure out how to build a slimmed down OG-USA (without the bloat of all the data for testing) before I try to build a conda-forge package for it. I've just updated the GH Action to install OG-USA via GitHub so that it can be imported for the CI tests.

[jdebacker]

@andersonfrailey I think this PR is ready for your review again. Tests passing. But I'm not sure of the best way to handle the issue of needing OG-USA as a dependency. Maybe we just keep this a branch of Tax-Brain until we have an OG-USA package on conda-forge?

[andersonfrailey]

@jdebacker, waiting until OG-USA is on conda-forge is probably the easiest option. Do you know if there's a way for us to include it as an optional dependency? So conda-forge would be able to build the package without it, but users would be notified that they need to install it separately if they try and use the OG-USA functionality