Fix the duplicate message in the discuss and search when the message type is email. This was caused by a wrong rebase of https://github.com/odoo/odoo/pull/118794 that did not take into account the branching on message body for message of type email by https://github.com/odoo/odoo/pull/131202 The search highlight feature was not working on these email message, so this commit also fixes that. closes odoo/odoo#138205 Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>