This intrinsic was only supported in fullcodegen, and is actually no
longer relevant for SunSpider peak performance it seems, so let's get
rid of it and maybe just implement Array.prototype.join with a fast
path at some point instead.

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/1708523002

Cr-Commit-Position: refs/heads/master@{#34084}