MAINT: remove glx env var, no longer needed and causing issues

[ZLLentz]

Description

Remove opengl-related environment variable from the conda startup scripts

Motivation and Context

At LCLS, this was a temporary workaround that is causing a new issue.

• This variable is causing https://jira.slac.stanford.edu/browse/ECS-5700
• This variable was originally a workaround for https://jira.slac.stanford.edu/browse/ECS-1867, see https://jira.slac.stanford.edu/browse/ECS-1878, MAINT: workaround for opengl crash when sshing to operator console #132, FIX: pcds_conda, dev_conda: only set mesa if renderer is failing #133
• Interactively, my applications no longer crash without this variable set: previously, even simply starting pydm would break everything.
• Now, sometimes I get a new OpenGL warning but no crashes.

In general, forcing the renderer settings in the conda environment sourceable led to a very confusing bug. This should have been handled (and seemingly has been handled) by adjusting the server settings.

I'm not sure why this variable is causing crashes now, but I am sure that I don't want to be in charge of messing with these sorts of settings in the future.

How Has This Been Tested?

Interactively only, as me

Where Has This Been Documented?

Only here and on Jira in https://jira.slac.stanford.edu/browse/ECS-5700

[tangkong]

🤷 This should really be outside of our wheelhouse, and this gets us closer to that