[IMP] theme_avantgarde: adapt s_banner

Since the redesign of the original banner snippet, the customizations
made in theme_avantgarde have had to be adapted.

task-3097005

Part-of: odoo/design-themes#687

theme_avantgarde/views/customizations.xml

@@ -223,11 +223,4 @@
     </xpath>
 </template>
 
-<!-- ======== BANNER ======== -->
-<template id="s_banner" inherit_id="website.s_banner" name="Avantgarde s_banner">
-    <xpath expr="//a[hasclass('btn')]" position="attributes">
-        <attribute name="class" add="btn-lg" separator=" "/>
-    </xpath>
-</template>
-
 </odoo>