Add v2 to coveosearchbox mf

Author: nginx-jack

layouts/_default/baseof.html

@@ -131,7 +131,7 @@
     <section class="base-layout">
       <section class="breadcrumb-layout">
         <div data-mf="true" id="searchbox" style="display:none;">
-          <div class="CoveoSearchbox" data-placeholder='Search NGINX Docs...'></div>
+          <div class="CoveoSearchbox-v2" data-placeholder='Search NGINX Docs...'></div>
         </div>
         {{ if not .IsHome }}
           {{ if not (in .Params.display_breadcrumb "false" ) }}