[FIX] purchase_stock: wrong deadline

Usecase to reproduce:
- Product A with Vendor supplier lead time=1day
- Product B with same Vendor supplier lead time=4days
- Launch the replenishment report for both products at the same time

Current Behavior:
The expected arrival is correct but the order date deadline is today - 3
days

Wanted Behavior:
Same but the order date dead line is today

It happens because it does the minimum of expected arrivals - max of
supplier delays. However the supplier delays are already correctly
apply on each procurement (correct expected arrival). To know the
correct order deadline we should instead take the minimum date planned
with the related supplier delay.

opw-2822588

closes odoo/odoo#90316

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