Minor doc fix: change truncating to rounding in TF32 docs (#49625)
Summary:
Minor doc fix in clarifying that the input data is rounded not truncated.
CC zasdfgbnm ngimel
Pull Request resolved: https://github.com/pytorch/pytorch/pull/49625
Reviewed By: mruberry
Differential Revision: D25668244
Pulled By: ngimel
fbshipit-source-id: ac97e41e0ca296276544f9e9f85b2cf1790d9985
