Delete hack that was once needed to fix the build

Summary:
Introduced in 6c7b41cc.

I checked the rest of that commit, and this is all that was left to revert.

Test Plan: x

Reviewers: ezyang, austin

Reviewed By: ezyang, austin

Subscribers: simonmar, ezyang, carter, thomie

Differential Revision: https://phabricator.haskell.org/D241