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

Committed: https://crrev.com/ccf12b4bede3f1ce3ce14fb33bcc4041525a40af
Cr-Commit-Position: refs/heads/master@{#34084}

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

Cr-Commit-Position: refs/heads/master@{#34146}