testsuite: update T6056 rule firing order

Fixes testsuite failure.

Summary: Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>

Test Plan: validate --slow

Reviewers: simonpj, austin

Reviewed By: austin

Subscribers: simonmar, ezyang, carter

Differential Revision: https://phabricator.haskell.org/D184