ac08da0a834631b2a7c39c40b1f36f01a85e8617 moved channel_type from Thread
to Channel, but data returned by get_mention_suggestions have not been
updated accordingly. This commit adapts it.
Follow-up of task-2948676.
closesodoo/odoo#98677
Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>