Check that block height and width are positive in `nn.Fold` (#69048)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/68875
cc albanD mruberry jbschlosser walterddr
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69048
Reviewed By: samdow
Differential Revision: D32729307
Pulled By: jbschlosser
fbshipit-source-id: 162cafb005873012d900d86997d07640967038c0
