MyoSuite methods not accessible without env.unwrapped under new Gymnasium versions

### Problem

When using MyoSuite environments through Gymnasium, custom MyoSuite methods
(e.g. `mj_render`) are no longer accessible directly on the environment object.

Example:

```python
from myosuite.utils import gym

env = gym.make('myoElbowPose1D6MRandom-v0')
env.reset()
env.mj_render()   # AttributeError
```

This only works via:
``` python
env.unwrapped.mj_render()
```