[FIX] point_of_sale: double dipping in COGS and stock delivered accounts

To reproduce:

1. Sell an anglo product (inventory valuation = automated) in the pos app.
2. Go back to the backend, find the pos.order and invoice it.
3. Close the session.
4. Open the journal items related to the session (click the Journal Items
button in the session form).
5. You will see COGS (Expenses) Account and Stock Interim (Delivered) are
debited in two journal entries - one from the invoice and one from the
created picking after the closing of session.

This is because we are not properly skipping the invoiced order when
generating the global picking for the session. This commit fixes the
described issue.

closes odoo/odoo#70374

Signed-off-by: pimodoo <pimodoo@users.noreply.github.com>