Commit 30af656e1a removed a third operand
in the domain but forgot to remove its operator, making the domain
filtering on the Participant invalid.
This commit fixes it by removing the ~~first~~ second pipe.
closes odoo/odoo#54504
X-original-commit: 44feadabab601b0df34d504b585abb9339a4a478
Signed-off-by: Christophe Simonis <chs@odoo.com>