Revert of [turbofan] Utilize String comparison feedback. (patchset #1 id:1 of https://codereview.chromium.org/2523463002/ )

Reason for revert:
Seems to regress speedometer on Ignition and doesn't cause any improvements elsewhere.

BUG=chromium:668651

Original issue's description:
> [turbofan] Utilize String comparison feedback.
>
> Make use of the previously introduced String feedback for compare
> operations in TurboFan.
>
> R=jarin@chromium.org
> BUG=v8:5267,v8:5400
>
> Committed: https://crrev.com/5d4253ecfb6ddcbbd7eb5654e728efa9559284a2
> Cr-Commit-Position: refs/heads/master@{#41163}

TBR=jarin@chromium.org,bmeurer@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=v8:5267,v8:5400

Review-Url: https://codereview.chromium.org/2531183003
Cr-Commit-Position: refs/heads/master@{#41324}