[FIX] stock_account: ctx after group by
[FIX] stock_account: ctx after group by

- Set valuation to FIFO
- Make a PO for a product
- Validate the picking
- Execute the Inventory Valuation report
- Apply group by Category
- Click on the 'Valuation' info button

A traceback occurs because of the usual `group_by` context key which is
kept.

opw-1918915

closes odoo/odoo#30313
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo