fix: remove non-existent branch_short_name field

- Removed branch_short_name field that references non-existent field
- This field was causing KeyError during module loading
- Resolves registry setup error in purchase_order model

Files modified:
- odex25_purchase/purchase_requisition_custom/models/purchase_order.py

Error fixed: KeyError: 'branch_short_name' during field setup

odex25_purchase/purchase_requisition_custom/models/purchase_order.py

@@ -131,12 +131,6 @@ class PurchaseOrderCustom(models.Model):
         store=True,
         readonly=True
     )
-    branch_short_name = fields.Char(
-        string='Branch',
-        related='branch_id.branch_short_name',
-        store=True,
-        readonly=True
-    )
     purpose = fields.Char()
     category_ids = fields.Many2many('product.category', string='Categories')
     committe_members = fields.One2many('committe.member', inverse_name='po_id')