update comments

Author: Molly Xu

src/torchcodec/decoders/_video_decoder.py

@@ -144,7 +144,6 @@ def __init__(
         if num_ffmpeg_threads is None:
             raise ValueError(f"{num_ffmpeg_threads = } should be an int.")
 
-        # Handle device=None by using the current default device
         if device is None:
             device = str(torch.get_default_device())
         elif isinstance(device, torch_device):

test/test_decoders.py

@@ -396,8 +396,8 @@ def test_device_instance(self):
         ],
     )
     def test_device_none_default_device(self, device_str):
-        # device=None should respect both torch.device() context manager
-        # and torch.set_default_device()
+        # VideoDecoder defaults to device=None, which should respect both
+        # torch.device() context manager and torch.set_default_device().
 
         # Test with context manager
         with torch.device(device_str):