[Sheriff] Revert "Turn on allocation site pretenuring."

This reverts commit r18547 for breaking the GC stress builders.

BUG=
TBR=hpayer@chromium.org

Review URL: https://codereview.chromium.org/136323002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18549 ce2b1a6d-e550-0410-aec6-3dcde31c8c00