Remove wow_helper.exe from win64 build

Not used and not built under win64.

R=kerz@google.com

Review URL: https://codereview.chromium.org/37793002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230561 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230561