[FIX] purchase_stock: remove useless qty conversion in report

To reproduce the issue:
1. In Settings, enable "Units of Measure"
2. Create a product P:
    - Type: Storable
    - Unit of Measure: Units
    - Purchase UoM: Dozens
3. Create a PO with 1 (Dozens) x P
4. Open the Forecasted Report of P

Error: The value of "Requests for quotation" is 144, it should be 12.
The quantity has been converted twice.

OPW-2744195

closes odoo/odoo#84091

X-original-commit: 524a1c597fd409a488bb6af37aca8248727691c1
Signed-off-by: William Henrotin (whe) <whe@odoo.com>
Signed-off-by: Adrien Widart <awt@odoo.com>

addons/purchase_stock/report/report_stock_forecasted.py

@@ -15,11 +15,7 @@ class ReplenishmentReport(models.AbstractModel):
         if warehouse_id:
             domain += [('order_id.picking_type_id.warehouse_id', '=', warehouse_id)]
         po_lines = self.env['purchase.order.line'].search(domain)
-        in_sum = 0
-        if po_lines:
-            product_uom = po_lines[0].product_id.uom_id
-            quantities = po_lines.mapped(lambda line: line.product_uom._compute_quantity(line.product_uom_qty, product_uom))
-            in_sum = sum(quantities)
+        in_sum = sum(po_lines.mapped('product_uom_qty'))
         res['draft_purchase_qty'] = in_sum
         res['draft_purchase_orders'] = po_lines.mapped("order_id").sorted(key=lambda po: po.name)
         res['draft_purchase_orders_matched'] = self.env.context.get('purchase_line_to_match_id') in po_lines.ids