[FX] Make some modifications to limitation section (#51928)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51928
Reviewed By: jamesr66a
Differential Revision: D26329664
Pulled By: Chillee
fbshipit-source-id: 94fd7b03ca53f48b1e4633a462c6e02bb0fd2f3c
