It's an unconnected switch. Removing this in http://crrev/c/1044287

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3a110584f2109557a524b284ba8659ee80fdcfb4

commit 3a110584f2109557a524b284ba8659ee80fdcfb4
Author: Peter K. Lee <pkl@chromium.org>
Date: Fri May 04 21:44:07 2018

Removed defunct and unused NewFeedbackKitEnabled experiment flag

We stopped using this key/value pair in Experimental.plist since
http://crrev/c/927457.

Bug:  839738 
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I93f91da8fdfa37e314047515c0d6784432ce18b2
Reviewed-on: https://chromium-review.googlesource.com/1044287
Reviewed-by: Eric Noyau <noyau@chromium.org>
Commit-Queue: Peter Lee <pkl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556208}
[modify] https://crrev.com/3a110584f2109557a524b284ba8659ee80fdcfb4/ios/chrome/browser/resources/Settings.bundle/Experimental.plist

#feedback-kit-v2 flag is available under chrome://flags and feature is enabled by default from M67.

Note: This crbug is unrelated to chrome://flags. It is specifically referring to the defunct switch in System Settings.