[omnibox-next] Use one-line layout for all suggestions in WebUI popup.

In order to align with the one-line layout used for suggestions rendered
in the Views Omnibox popup, this CL updates the relevant logic to switch
from a two-line layout to a one-line layout in the WebUI Omnibox popup.

Bug: 445750270
Change-Id: Ic842e5b8ca788b341a172277d9eb1fcb8f427cb7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6968653
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Commit-Queue: Khalid Peer <khalidpeer@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1519618}