Remove leftover after refactoring

Author: diegoferigo-rai

newton/_src/viewer/viewer_gl.py

@@ -431,7 +431,7 @@ def end_frame(self):
         destroyed results in a crash (access violation).  Therefore we check
         whether an exit was requested and early-out before touching GL if so.
         """
-        return self._update()
+        self._update()
 
     @override
     def apply_forces(self, state):