For M65 I added a fast-path for String.p.charCodeAt, which behaves
incorrectly for wide characters. This patch disables the incorrect
fast-path. This is likely no performance regression against M64,
as M64 did not have a fast path for String.p.charCodeAt.

Bug: v8:7371
Change-Id: I8ea9c5da5a583138d87ccb8ffe6d61eba16630b9
Reviewed-on: https://chromium-review.googlesource.com/886782
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50873}