[docs] Correct errata in linalg.eigh and add a bit more information (#59784)
Summary:
Add extra information about the returned elements of the spectral
decompositions
Resolves https://github.com/pytorch/pytorch/issues/59718
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59784
Reviewed By: soulitzer
Differential Revision: D29088998
Pulled By: mruberry
fbshipit-source-id: 58a191c41ff5e4c9d9675e5b3d7cbbcf16be4da1
