[Doc] Fix the return type for load functions (#1122)

torchaudio/backend/_soundfile_backend.py

@@ -104,7 +104,7 @@ def load(
             Not used. PySoundFile does not accept format hint.
 
     Returns:
-        torch.Tensor:
+        Tuple[torch.Tensor, int]: Resulting Tensor and sample rate.
             If the input file has integer wav format and normalization is off, then it has
             integer type, else ``float32`` type. If ``channels_first=True``, it has
             ``[channel, time]`` else ``[time, channel]``.

torchaudio/backend/sox_io_backend.py

@@ -107,7 +107,7 @@ def load(
             from header or extension,
 
     Returns:
-        torch.Tensor:
+        Tuple[torch.Tensor, int]: Resulting Tensor and sample rate.
             If the input file has integer wav format and normalization is off, then it has
             integer type, else ``float32`` type. If ``channels_first=True``, it has
             ``[channel, time]`` else ``[time, channel]``.