[FIX] mail: mention a channel from a channel

Before this commit, when mentioning a channel from a channel,
it crashed with following error:

```
TypeError: unhashable type: 'list'
```

This commit fixes the issue by providing a list of channel ids,
instead of a list of `[4, channelID]`, when mentioning channels.

closes odoo/odoo#36359

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

addons/mail/static/src/js/models/threads/thread.js

@@ -345,9 +345,7 @@ var Thread = AbstractThread.extend(ServicesMixin, {
         body = this._generateEmojis(body);
         var messageData = {
             partner_ids: data.partner_ids,
-            channel_ids: _.map(data.channel_ids, function (channelID) {
-               return [4, channelID, false];
-            }),
+            channel_ids: data.channel_ids,
             body: body,
             attachment_ids: data.attachment_ids,
             canned_response_ids: data.canned_response_ids,