clean up the flag in OmniboxResourceProvider

UX revamp phrase 2 launched, so this CL clean up the params
modernize_visual_update_active_color_on_omnibox for the
OMNIBOX_MODERNIZE_VISUAL_UPDATE.

Change-Id: Ie20348f54a2b442f044549ae00d3534d279f6639
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5388429


Auto-Submit: Gang Wu <gangwu@chromium.org>
Commit-Queue: Tomasz Wiszkowski <ender@google.com>
Reviewed-by: Tomasz Wiszkowski <ender@google.com>
Cr-Commit-Position: refs/heads/main@{#1277338}