Remove separators from panda_nohand.xml default classes

[peterdavidfagan]

I encountered an error when migrating to the robot_descriptions package related to reading official mjcf files that contain separators in class names. Further details of this issue can be found here.

This pull request updates the panda_nohand.xml model by renaming default class names to ensure the model can be read using the dm_control.mjcf API.

[kevinzakka]

Hi @peterdavidfagan, my usual way of loading this model is as follows:

panda_mjcf = mjcf.from_path(PANDA_NO_HAND_XML.as_posix(), escape_separators=True)

Agreed though that it's better to be consistent across all models so going to approve this PR.

[peterdavidfagan]

Thanks @kevinzakka the above is working for me, not sure how I missed the escape_parameters argument. Thanks for this clarification.

[kevinzakka]

Hi @peterdavidfagan, I think this broke a few dependencies in MuJoCo MPC so going to close for now.

[peterdavidfagan]

Thanks for letting me know @kevinzakka and ok sounds good.