Pin MuJoCo for LIBERO rendering compatibility

[JiahuiKChen]

Summary

Pin mujoco==3.3.2 in requirements.txt.

Issue Fixed

I encountered issues using LIBERO with MuJoCo > 3.3.2, where eval-time rendering of images appear different from the original training images. Floors appear darker and introducing a distribution shift, causing evaluation success rate degredation.
Issue #88 reports the same thing: that MuJoCo 3.3.3 changes LIBERO-Object rendering, making floors appear darker.
Issue #87 shows similar image rendering issues.

The workaround is to downgrade to MuJoCo 3.3.2, which seems to restore the original rendering. Since this repo already pins related simulation dependencies such as robosuite==1.4.0, pinning MuJoCo here keeps evaluation environments reproducible.

Fixes #88.

Pinning choice

This PR uses a hard pin to mujoco==3.3.2 because this version seemed to fixed my evaluation issues and was also the fix in Issue #88 .

If the authors/maintainers know the exact MuJoCo version used to generate the training data, pinning that version would be the best.

Validation

• Dependency-only change.
• Running evals with this mujoco version fixed my evaluation performance degradation.