[FIX] product_expiry: fix expiration date on stock move line

To Reporduce
=============
- Install inventory, purchase and product_expiry
- Create a new storable product that is tracked by lots or serial numbers and expiration date and set expiration days to a value
- Go to inventory > configuration > Warehouse Management > Operations Types
- In “San Francisco: Receipts” > Enable "Create New Lots/Serial Numbers"
- Create a new RFQ > select the created product > Confirm the order
- Click on “Receipt”
- Click on the icon with 3 bars (last thing on line) to open Detailed Operations view
- add a line and set a `lot/serial Number`
- from the same view open the `lot/serial number` wizard and edit the expiration the date
- save/confirm

Problem
=======
The expiration date on Detailed Operations doesn't change

Solution
=========
to solve the issue a condition in compute method was corrected

opw-2937438

closes odoo/odoo#97898

Signed-off-by: William Henrotin (whe) <whe@odoo.com>