tensor_illustration with correct numbers and better fonts for README file (#20751)
Summary:
Fix of README tensor image for issue #20641
Numbers are fixed, symbols made more readable.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20751
Differential Revision: D15495706
Pulled By: ezyang
fbshipit-source-id: b6013574d16253ec681fc57143efe3d53952fbe9
