Revert "[ios] Enable WebKit based side swipe with Chrome side swipe."

This reverts commit 60efce525699139770f5d516fe80e3584d1d2a94.

Reason for revert: Lots of tests are failing with a segfault in SideSwipeController updateNavigationEdgeSwipeForWebState; e.g., https://chromium-swarm.appspot.com/task?id=4176d009da672b10&refresh=10&show_raw=1

Original change's description:
> [ios] Enable WebKit based side swipe with Chrome side swipe.
> 
> Enables WebKit based side swipe, and only enables Chrome side swipe when the
> page swiped page is to or from an NTP.
> 
> Change-Id: I892f7074252ee04b2d0b337ebd744f3ba9388e27
> Reviewed-on: https://chromium-review.googlesource.com/c/1350192
> Commit-Queue: Justin Cohen <justincohen@chromium.org>
> Reviewed-by: Eugene But <eugenebut@chromium.org>
> Reviewed-by: Danyao Wang <danyao@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#612042}

TBR=justincohen@chromium.org,eugenebut@chromium.org,danyao@chromium.org

Change-Id: I00da0d289307497cdc2f49ab4b6336316d345259
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/1355039
Reviewed-by: Greg Thompson <grt@chromium.org>
Commit-Queue: Greg Thompson <grt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612145}
8 files changed