Do not test max_bytes_used et. al for haddock tests

Summary: as these are unreliable, and it is hard to re-run haddock with other RTS flags.

Test Plan: run validate

Reviewers: austin

Subscribers: simonmar, ezyang, carter

Differential Revision: https://phabricator.haskell.org/D196

GHC Trac Issues: #9551