[FIX] mrp: correctly copy non-backordered MO

Steps to reproduce:
Step 1: make a MO and create less than the quantity to produce
Step 2: Mark As Done (with no backorder)
Step 3: duplicate the MO and try to change the quantity to produce

Expected result: qty to produce changes as expected
Actual result: server error

Issue is due to the copied MO's `move_finished_ids` including a copy
of the cancelled finished move (i.e. the qty not backordered) so there
were 2 `move_finished_ids` for the product to produce. This resulted in
an access error since the onchange to update the `move_finished_ids`
only expects 1 move for the product to produce and results in a
singleton error.

Issue 2 of Task: 2618962

closes odoo/odoo#74864

Signed-off-by: Arnold Moyaux <amoyaux@users.noreply.github.com>