[FIX] website: do not translate code

Header of XML files should not be translated.
Before this commit, some users may translate the XML header and get
invalid XML if translating words like "encoding"

Fixes odoo/odoo#82155

closes odoo/odoo#82439

X-original-commit: aaac6fc04f4e5aa4c9ad68d9e844f3e786044800
Signed-off-by: Martin Trigaux (mat) <mat@odoo.com>

addons/website/views/website_templates.xml

@@ -2135,7 +2135,7 @@
     </script>
 </template>
 <template id="default_xml">
-    &lt;?xml version="1.0" encoding="utf-8"?&gt;
+    <t t-translation="off">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</t>
 </template>
 <template id="default_css">
     <style type="text/css">
@@ -2159,7 +2159,7 @@
     </style>
 </template>
 <template id="default_csv">
-    1,2,3
+    <t t-translation="off">1,2,3</t>
 </template>
 
 <!-- PAGE 404 -->
@@ -2336,18 +2336,19 @@ Sitemap: <t t-esc="url_root"/>sitemap.xml
     </url>
 </template>
 
-<template id="sitemap_xml">&lt;?xml version="1.0" encoding="UTF-8"?&gt;
+<template id="sitemap_xml"><t t-translation="off">&lt;?xml version="1.0" encoding="UTF-8"?&gt;</t>
 <urlset t-attf-xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
     <t t-out="content"/>
 </urlset>
 </template>
 
-<template id="sitemap_index_xml">&lt;?xml version="1.0" encoding="UTF-8"?&gt;
+<template id="sitemap_index_xml"><t t-translation="off">&lt;?xml version="1.0" encoding="UTF-8"?&gt;
 <sitemapindex t-attf-xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
   <sitemap t-translation="off" t-foreach="pages" t-as="page">
     <loc><t t-esc="url_root"/>sitemap-<t t-esc="page"/>.xml</loc>
   </sitemap>
 </sitemapindex>
+</t>
 </template>
 
 <template id="website_search_box" name="Website Searchbox">