fixed the first line of torch.rst to match the __init__.py file's first line (#49584)

Summary:
Changed the first line of the torch.rst file to match that of the __init__.py file

Fixes https://github.com/pytorch/pytorch/issues/49228

Pull Request resolved: https://github.com/pytorch/pytorch/pull/49584

Reviewed By: VitalyFedyunin

Differential Revision: D25639260

Pulled By: mrshenli

fbshipit-source-id: a0bafd945ff92115eed932662feedc46d29dfaab
diff --git a/docs/source/torch.rst b/docs/source/torch.rst
index 2bb6c02..440cbdb 100644
--- a/docs/source/torch.rst
+++ b/docs/source/torch.rst
@@ -1,7 +1,7 @@
 torch
 =====
 The torch package contains data structures for multi-dimensional
-tensors and mathematical operations over these are defined.
+tensors and defines mathematical operations over these tensors.
 Additionally, it provides many utilities for efficient serializing of
 Tensors and arbitrary types, and other useful utilities.