[turbofan] Drop obsolete test after r24236.

This was missing from the previous commit.

TBR=jarin@chromium.org

Review URL: https://codereview.chromium.org/602193005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24237 ce2b1a6d-e550-0410-aec6-3dcde31c8c00