[IMP] mrp: change scheduled date unplan workorders

With this commit, changing the scheduled date on a planned production
order will unplan the workorders and so highlight the 'Plan' button to
replan them from the new scheduled date.

closes odoo/odoo#71089

X-original-commit: a6783acaef3c7c2224d1cda72717a36c4b38c001
Signed-off-by: Rémy Voet <ryv-odoo@users.noreply.github.com>