Fix typo (#1759)

Co-authored-by: Holly Sweeney <77758406+holly1238@users.noreply.github.com>

Author: Aashwin2202

beginner_source/former_torchies/autograd_tutorial_old.py

@@ -120,7 +120,7 @@
 print(x.grad)
 
 ###############################################################
-# You can also stops autograd from tracking history on Tensors
+# You can also stop autograd from tracking history on Tensors
 # with requires_grad=True by wrapping the code block in
 # ``with torch.no_grad():``
 print(x.requires_grad)