[FIX] mrp: set default product on unbuild order

Before this commit, Creating Unbuild order using
 Unbuild Button was resetting Bom as it was calling
`_onchange_product_id` after setting `mo_id` which was
resetting Bom on Unbuild order.

To Fix Issue, We setting `default_product_id` so It would not
reset `bom_id` when `_onchange_product_id` is called.

Fixes: #70216
Odoo Ticket: 2521788

closes odoo/odoo#70304

X-original-commit: 4de0ae434d1adc97fc1077b8d0f23c7e800ec161
Signed-off-by: Rémy Voet <ryv-odoo@users.noreply.github.com>

addons/mrp/models/mrp_production.py

@@ -1622,7 +1622,8 @@ class MrpProduction(models.Model):
             'res_model': 'mrp.unbuild',
             'view_id': self.env.ref('mrp.mrp_unbuild_form_view_simplified').id,
             'type': 'ir.actions.act_window',
-            'context': {'default_mo_id': self.id,
+            'context': {'default_product_id': self.product_id.id,
+                        'default_mo_id': self.id,
                         'default_company_id': self.company_id.id,
                         'default_location_id': self.location_dest_id.id,
                         'default_location_dest_id': self.location_src_id.id,