fixed minatar example

[yutaizhou]

examples/brax_minatar.ipynb imports a version of LogEnvState and LogWrapper from gymnax that does not support timestep logging, so the notebook does not run successfully.

This commit adds the newer definition of those two classes from purejaxrl/wrappers.py into the notebook to make it run successfully.

I only made this PR to raise awareness of the issue. I am not too familiar with the code base yet, so it's possible that I made a bunch of redundant imports.

Thank you for the wonderful blog post! To me, this is the "4 minute mile" equivalent of showing the cool possibilities of speeding up RL using jax :)

[luchris429]

Thanks Yutai! I'll get around back to this next week -- I don't think I can merge in the PR as-is since the notebook output hasn't been cleaned.