Fix a typo
Fix a typo

Reviewers: goldfire, bgamari, RyanGlScott

Reviewed By: RyanGlScott

Subscribers: rwbarton, thomie, carter

GHC Trac Issues: #15406

Differential Revision: https://phabricator.haskell.org/D4976

sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc