Revert "[DCP] Add FsspecReader and FsspecWriter to checkpoint __init__.py (#105088)"
This reverts commit 76a053d55cb23948c7b331a48f921744db24601e.
Reverted https://github.com/pytorch/pytorch/pull/105088 on behalf of https://github.com/atalman due to broke trunk and linux-focal-py3.9-clang7-asan ([comment](https://github.com/pytorch/pytorch/pull/105088#issuecomment-1633385350))
