[IMP] fleet: prevent deprecated warning message

Stop "required=True is deprecated: making a boolean field"
appearing in server log

Closes #6108
opw-632480

addons/fleet/fleet.py

@@ -66,7 +66,7 @@ class fleet_vehicle_cost(osv.Model):
         'odometer_unit': fields.related('vehicle_id', 'odometer_unit', type="char", string="Unit", readonly=True),
         'date' :fields.date('Date',help='Date when the cost has been executed'),
         'contract_id': fields.many2one('fleet.vehicle.log.contract', 'Contract', help='Contract attached to this cost'),
-        'auto_generated': fields.boolean('Automatically Generated', readonly=True, required=True),
+        'auto_generated': fields.boolean('Automatically Generated', readonly=True),
     }
 
     _defaults ={