(Backport : fbf76c1f)

Expected behavior : Quantities are displayed in the same way on the delivery note regardless the stock picking stage.

Current behavior : Quantities aren't displayed in the same way on the delivery note depending on the stock picking stage. (e.g. `2.00 Units` units when picking is in `Waiting` stage but `2.0 Units` when picking is in `Done` stage)

Steps to reproduce the error :
- Create a RFQ with few units of a Storable Product (e.g. 2 units)
- Go to the Receipt and print the Delivery Slip and look at the quantities printed (e.g. 2.00)
- Validate the Receipt and print the Delivery Slip again, quantities printed have changed (e.g. 2.0)

opw-2578120

closes odoo/odoo#78815

Signed-off-by: Arnold Moyaux <arm@odoo.com>