Clarify wording around overrides subclasses. (#51031)

Summary:
Fixes #47117

Pull Request resolved: #51031

Reviewed By: bdhirsh

Differential Revision: D26047498

Pulled By: albanD

fbshipit-source-id: dd0a7d9f97c0f6469b3050d2e3b4473f1bee3820

docs/source/notes/extending.rst

@@ -486,7 +486,8 @@ of a function from ``torch.Tensor`` subclasses, they must use
 
 Subclassing ``torch.Tensor``
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-As of version 1.7.0, methods and functions applied on ``torch.Tensor`` subclasses
+As of version 1.7.0, methods on ``torch.Tensor`` and functions in public
+``torch.*`` namespaces applied on ``torch.Tensor`` subclasses
 will return subclass instances instead of ``torch.Tensor`` instances::
 
   >>> class SubTensor(torch.Tensor):