Settings: Fix runtime error when searching on CrOS.

Fixes the following runtime error:
"Uncaught Error: Assertion failed: An associated control was expected
for SETTINGS-SUBPAGE Manage spell check, but was not found."

which was thrown when searching on chrome://settings on CrOS, because
of the isChromeOSLanguagesSettingsUpdate_ flag not being applied to
the settings-edit-dictionary-page subpage.

Bug: 1179104
Change-Id: Ie3e25c537c5d0dd52bfb46620ed3c28bf329fe38
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2775470


Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: dpapad <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#865076}