[REM] web: remove condition comments targeting old IE versions

As we don't support anymore Internet Explorer browser, we can safely
remove conditional comments targetting older versions of it (and even
not supported in IE since version 10).

Also, when executed, this could have added a second `<body>` tag (which
is not valid HTML document).

References:
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/body
https://en.wikipedia.org/wiki/Conditional_comment

closes odoo/odoo#47170

Signed-off-by: Adrien Dieudonné (adr) <adr@odoo.com>

addons/web/views/webclient_templates.xml

@@ -861,12 +861,6 @@
                 <t t-call-assets="web.assets_backend" t-css="false"/>
                 <t t-call="web.conditional_assets_tests"/>
 
-                <![CDATA[
-                    <!--[if lt IE 10]>
-                        <body class="ie9">
-                    <![endif]-->
-                ]]>
-
                 <script type="text/javascript" src="/web/static/src/js/main.js"></script>
             </t>
             <t t-set="head" t-value="head_web + (head or '')"/>