[FIX] mail: mark all messages as read in discuss inbox

Revision on https://github.com/odoo/odoo/commit/a55c78836f172dba1cfa6db3df0e927a9c7e6471



Before this commit, marking all messages as read from Discuss inbox
did not update the UI correctly, hence requiring a page reload.

This bug comes from a typo in the commit above, which passed a list
of mail_notification instead of message ids, so that messages were
handled as marked as read by the web client.

Task-Id 2158452

closes odoo/odoo#43109

X-original-commit: 3cc03ee3db90c310dc60fe7ea18e0e6abe741ffa
Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>