Fix torch.nn.functional.gelu docstring formatting (#89061)
The docstring of `torch.nn.functional.gelu` is formatted incorrectly, so that part of the math isn't rendered and there are extra blocks when there shouldn't: https://pytorch.org/docs/stable/generated/torch.nn.functional.gelu.html
I didn't build the docs, so I am not 100% sure that I got the formatting right, but I am confident.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/89061
Approved by: https://github.com/bdhirsh, https://github.com/kit1980
