change ExecuteFirmwareManagementRequest async

EVCB_OCPP.WSServer/Message/FirmwareManagementProfileHandler.cs

@@ -73,7 +73,7 @@ namespace EVCB_OCPP.WSServer.Message
                                             OutRequest: _updateFWrequest,
                                             SerialNo: requestId);
 
-                                        var clearMachine = db.Machine.Where(x => x.Id == machine.Id).FirstOrDefault();
+                                        var clearMachine = await db.Machine.Where(x => x.Id == machine.Id).FirstOrDefaultAsync();
                                         clearMachine.FW_AssignedVersion = null;
                                         await db.SaveChangesAsync();
                                     }