[FIX] sale_timesheet: extract the check on write in a function
[FIX] sale_timesheet: extract the check on write in a function

On write, a check is done that raises
'You can not modify already invoiced timesheets …'.
We put that check in a function so that this behaviour can be extended.
(restricted by an override, or relaxed by not calling the super)

opw 1974968
closes #33057

closes odoo/odoo#33092

Signed-off-by: Nans Lefebvre (len) <a573b540d2dde90ba6da3b9d6286c8ec60c10044@odoo.com>
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo