[FIX] rma: Use Form to avoid UoM change invalid check

Since odoo/odoo#75823, the wizard lines have the field uom_id related to
move.product_uom and readonly=False, so if you call directly to
wiz.onchage_picking_id a write in stock move is executed and the warning raises,
although we don't really do any UoM change.

We avoid it using the `Form` to perform the wizard update.

rma/models/rma.py

@@ -895,15 +895,14 @@ class Rma(models.Model):
                 location_id=self.location_id.id,
                 picking_id=self.picking_id.id,
             )
-        return_wizard = (
-            self.env["stock.return.picking"]
-            .with_context(
-                active_id=self.picking_id.id,
+        stock_return_picking_form = Form(
+            self.env["stock.return.picking"].with_context(
                 active_ids=self.picking_id.ids,
+                active_id=self.picking_id.id,
+                active_model="stock.picking",
             )
-            .create(create_vals)
         )
-        return_wizard._onchange_picking_id()
+        return_wizard = stock_return_picking_form.save()
         return_wizard.product_return_moves.filtered(
             lambda r: r.move_id != self.move_id
         ).unlink()