fix pusht images type from float32 to uint8, update gym-pusht dependencies

tests/test_datasets.py

@@ -51,6 +51,7 @@ def test_factory(env_name, dataset_id, policy_name):
         keys_ndim_required.append(
             (key, 3, True),
         )
+        assert dataset.data_dict[key].dtype == torch.uint8, f"{key}"
     
     # test number of dimensions
     for key, ndim, required in keys_ndim_required: