Fix typographical error in torch.triu docstring (pytorch#32067) (pytorch#32122)

Summary:
below --> above

Fixes pytorch#32032
Pull Request resolved: pytorch#32067

Differential Revision: D19355788

Pulled By: zou3519

fbshipit-source-id: dc7a2538a78cd11e72d47ad923ef50599a5a87e2

Author: vishwakftw

torch/_torch_docs.py

@@ -5788,7 +5788,7 @@ def merge_dicts(*dicts):
 above the diagonal.
 
 The argument :attr:`diagonal` controls which diagonal to consider. If
-:attr:`diagonal` = 0, all elements on and below the main diagonal are
+:attr:`diagonal` = 0, all elements on and above the main diagonal are
 retained. A positive value excludes just as many diagonals above the main
 diagonal, and similarly a negative value includes just as many diagonals below
 the main diagonal. The main diagonal are the set of indices