[FIX] im_livechat: fix cors error on embed livechat

Before this commit, starting a page with the livechat embed
in another origin than Odoo would have resulted in an CORS
error being shown due to the `bootstrap_translation` route
being called in response to the legacy `web.session` setup.

This commit restore the legacy session as it was before [1].

[1]: https://github.com/odoo/odoo/pull/122834

closes odoo/odoo#125565

Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/im_livechat/__manifest__.py

@@ -106,7 +106,6 @@ Help your customers with this chat, and analyse their feedback.
             ('remove', 'web/static/src/legacy/js/common_env.js'),
             'web/static/src/views/fields/formatters.js',
             'web/static/src/views/fields/file_handler.*',
-            'web/static/src/legacy/js/services/session.js',
             'bus/static/src/bus_parameters_service.js',
             ('remove', 'bus/static/src/services/assets_watchdog_service.js'),
 

addons/im_livechat/static/src/embed/external/session_legacy.js

@@ -0,0 +1,6 @@
+/* @odoo-module alias=web.session */
+
+import Session from "web.Session";
+import { serverUrl } from "@im_livechat/embed/livechat_data";
+
+export default new Session(undefined, serverUrl, { use_cors: true });