This is one place that I've missed with D1862.
This doesn't fix the underlying problem and I prefer to suppress it
now and fix it later as this is a part of a larger effort (#11371)
to fix an old bug with `substTy` called with invalid `in_scope` sets.

Test Plan: `make test TEST="hClose002 hClose003 hDuplicateTo001"

Reviewers: thomie, austin, bgamari, trofi

Reviewed By: trofi

Differential Revision: https://phabricator.haskell.org/D1872

GHC Trac Issues: #11371