[Doc] Fix a word in documents (#3334)

Summary:
A redundant "and" just removed.

Pull Request resolved: https://github.com/pytorch/audio/pull/3334

Reviewed By: xiaohui-zhang

Differential Revision: D45864314

Pulled By: mthrok

fbshipit-source-id: ad67bde8fa73eac995fbd0d3809709cc38486884

torchaudio/transforms/_transforms.py

@@ -509,7 +509,7 @@ class MelSpectrogram(torch.nn.Module):
 
     .. properties:: Autograd TorchScript
 
-    This is a composition of :py:func:`torchaudio.transforms.Spectrogram` and
+    This is a composition of :py:func:`torchaudio.transforms.Spectrogram`
     and :py:func:`torchaudio.transforms.MelScale`.
 
     Sources