Settings: change setting label from <p> to <div> to match other labels

Bug: 867193
Change-Id: I140d9b979ba7f58a3ab8e62142797caddd148f44
Reviewed-on: https://chromium-review.googlesource.com/1154195Reviewed-by: Scott Chen <scottchen@chromium.org>
Commit-Queue: Esmael El-Moslimany <aee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579201}

chrome/browser/resources/settings/search_page/search_page.html

@@ -47,9 +47,9 @@
         <!-- Omnibox search engine -->
         <div class="settings-box first block">
           <div id="search-wrapper">
-            <p id="searchExplanation" class="start">
+            <div id="searchExplanation" class="start">
               $i18nRaw{searchExplanation}
-            </p>
+            </div>
             <template is="dom-if" if="[[isDefaultSearchControlledByPolicy_(
                 prefs.default_search_provider_data.template_url_data)]]">
               <cr-policy-pref-indicator pref="[[