Nest voice match under "Ok Google" in Settings.

Bug: b:141990654
Change-Id: I249a7bf9fb124877a540760d4e547f9f0d4b9a7e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1836138Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/master@{#702173}

chrome/browser/resources/settings/google_assistant_page/google_assistant_page.html

@@ -87,7 +87,7 @@
           </select>
         </div>
         <template is="dom-if" if="[[shouldShowVoiceMatchSettings_]]">
-          <div class="settings-box">
+          <div class="settings-box continuation embedded">
             <div class="start text-area settings-box-text">
               <div class="label">
                 $i18n{googleAssistantVoiceSettings}