directbase: fix a stray pandac.PandaModules

direct/src/directbase/ThreeUpStart.py

@@ -1,7 +1,7 @@
 
 print('ThreeUpStart: Starting up environment.')
 
-from pandac.PandaModules import *
+from panda3d.core import *
 
 from direct.showbase.PythonUtil import *
 from direct.showbase import ThreeUpShow