Disable macOS Apple Silicon mujoco tests for now

tests/algo/test_learner.py

@@ -14,6 +14,7 @@
 from sample_factory.cfg.arguments import verify_cfg
 from sample_factory.utils.attr_dict import AttrDict
 from sample_factory.utils.dicts import iterate_recursively
+from sf_examples.mujoco.mujoco_utils import mujoco_available
 from sf_examples.mujoco.train_mujoco import parse_mujoco_cfg, register_mujoco_components
 
 
@@ -38,6 +39,7 @@ def _learner_losses_res(learner: Learner, dataset: AttrDict, num_invalids: int)
     )
 
 
+@pytest.mark.skipif(not mujoco_available(), reason="mujoco not installed or not available on this machine")
 class TestValidMasks:
     @pytest.fixture(scope="class", autouse=True)
     def register_mujoco_fixture(self):