fix(handler): scope the background session deletion error

The retry callback assigned to the enclosing if-scoped err instead of
declaring its own. Nothing read that variable after the handler
returned, so behaviour is unchanged.

pkg/handler/handler.go

@@ -430,7 +430,7 @@ func (s *Standalone) LogoutFrontChannel(w http.ResponseWriter, r *http.Request)
 		go func() {
 			// attempt background delete with retries
 			err := retry.Do(context.Background(), func(ctx context.Context) error {
-				err = s.SessionManager.DeleteForExternalID(ctx, sid)
+				err := s.SessionManager.DeleteForExternalID(ctx, sid)
 				if err == nil || errors.Is(err, session.ErrNotFound) {
 					return nil
 				}