Remove broken ref to travis_haskell cookbook
Remove broken ref to travis_haskell cookbook

travis-ci/travis-cookbooks,ljharb/travis-cookbooks,travis-ci/travis-cookbooks,ljharb/travis-cookbooks,travis-ci/travis-cookbooks,ljharb/travis-cookbooks,spurti-chopra/travis-cookbooks,spurti-chopra/travis-cookbooks,spurti-chopra/travis-cookbooks