char: Remove references to dead "ComputedVertices" class

This hasn't been a thing for nearly 13 years.

panda/src/char/character.h

@@ -30,7 +30,6 @@
 #include "sliderTable.h"
 
 class CharacterJointBundle;
-class ComputedVertices;
 
 /**
  * An animated character, with skeleton-morph animation and either soft-

panda/src/char/characterJoint.cxx

@@ -60,7 +60,7 @@ CharacterJoint(Character *character,
   // update_internals() to get our _net_transform set properly.
   update_internals(root, parent, true, false, current_thread);
 
-  // And then compute its inverse.  This is needed for ComputedVertices,
+  // And then compute its inverse.  This is needed for JointVertexTransform,
   // during animation.
   _initial_net_transform_inverse = invert(_net_transform);
 }