The Proxy enumerate trap and Reflect.enumerate are removed from the
ES2016 draft specification. This patch removes the Reflect.enumerate
function, and a follow-on patch will be responsible for the Proxy
trap changes.

R=adamk
LOG=Y
BUG=v8:4768

Review URL: https://codereview.chromium.org/1721453002

Cr-Commit-Position: refs/heads/master@{#34196}