Fix FFT documentation examples and run doctests in the test suite (#60304)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/59514
Pull Request resolved: https://github.com/pytorch/pytorch/pull/60304
Reviewed By: anjali411
Differential Revision: D29253980
Pulled By: mruberry
fbshipit-source-id: 0654f00197e5fae338aa8edf0b61ef5692cdaa7e
