testsuite: Rip out hack for #12554

@Phyx is working on correctly fixing (pun intended) the underlying issue
that prompted this hack. It turns out that `timeout` it the culprit.
Moreover, this hack breaks on msys python builds, which don't export
`WindowsError`.

Test Plan: Validate on Windows with `msys` python.

Reviewers: Phyx, austin

Subscribers: thomie, Phyx

Differential Revision: https://phabricator.haskell.org/D2724

GHC Trac Issues: #12554