Remove FAIL from test262-es6.status

TBR=rossberg
BUG=v8:3642
LOG=Y

Review URL: https://codereview.chromium.org/698073003

Cr-Commit-Position: refs/heads/master@{#25088}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25088 ce2b1a6d-e550-0410-aec6-3dcde31c8c00