[FIX] mrp : BoM report

Current behavior:
When creating a BOM with quantity different than 1 (here 12) with operation duration 1 minute and work center capacity 23
The BoM Structure & Cost report only changes the time for the operation when the quantity is > 276
However, when planning a MO the expected duration changes to 2 minutes when the quantity is > 23

Expected behavior:
Expected duration should be the same in the MO and BoM report

Steps to reproduce:
- BOM with quantity different than 1 (here 12)
- operation duration 1 minute
- work center capacity 23
- go in BoM report

closes odoo/odoo#79241

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