Fix assert_is_mobject_method when using OpenGL (ManimCommunity#2655)

Co-authored-by: Benjamin Hackl <[email protected]>

Author: trickypr

manim/animation/updaters/mobject_update_utils.py

@@ -20,12 +20,13 @@
 
 from manim.constants import DEGREES, RIGHT
 from manim.mobject.mobject import Mobject
+from manim.opengl import OpenGLMobject
 
 
 def assert_is_mobject_method(method):
     assert inspect.ismethod(method)
     mobject = method.__self__
-    assert isinstance(mobject, Mobject)
+    assert isinstance(mobject, (Mobject, OpenGLMobject))
 
 
 def always(method, *args, **kwargs):