Fix typo in LSTMCell document (#43395)
Summary:
Fixes typo in document
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43395
Reviewed By: mruberry
Differential Revision: D23312561
Pulled By: ngimel
fbshipit-source-id: 28340c96faf52c17acfe9f6b1dd94b71ea4d60ce
