Revert "ES6: Add support for Map/Set forEach"

This reverts commit https://code.google.com/p/v8/source/detail?r=20781.

It broke the Win32 builders.

TBR=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/239163012

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20782 ce2b1a6d-e550-0410-aec6-3dcde31c8c00