[FIX] mail_group: update template to QWeb

Steps to reproduce:
------------------
- Have Website and Mail Group installed
- Send Guidelines for a mailing list through the Website app

Issue
-----
{{ object.mail_group_id.name }} appears in the body of the "Mail Group: Send Guidelines" mail template instead of the actual mail group name.

opw-3778512

closes odoo/odoo#157772

X-original-commit: fe05e7c6acf02986a154af1235ac244a7686b30b
Signed-off-by: Tanguy Quéguineur (taqu) <taqu@odoo.com>
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/mail_group/data/mail_template_data.xml

@@ -9,7 +9,7 @@
         <field name="body_html" type="html">
             <div>
                 <p>Hello <t t-out="object.partner_id.name or ''"></t>,</p>
-                <p>Please find below the guidelines of the {{ object.mail_group_id.name }} mailing list.</p>
+                <p>Please find below the guidelines of the <t t-out="object.mail_group_id.name"></t> mailing list.</p>
                 <p><t t-out="object.mail_group_id.moderation_guidelines_msg or ''"></t></p>
             </div>
         </field>

addons/mail_group/i18n/mail_group.pot

@@ -58,7 +58,7 @@ msgstr ""
 msgid ""
 "<div>\n"
 "                <p>Hello <t t-out=\"object.partner_id.name or ''\"></t>,</p>\n"
-"                <p>Please find below the guidelines of the {{ object.mail_group_id.name }} mailing list.</p>\n"
+"                <p>Please find below the guidelines of the <t t-out=\"object.mail_group_id.name\"></t> mailing list.</p>\n"
 "                <p><t t-out=\"object.mail_group_id.moderation_guidelines_msg or ''\"></t></p>\n"
 "            </div>\n"
 "        "