See #5799. Fix segfault in upstream Blender when unlinking material objects in specific scenario.

I can't explain this one so I'm pretty embarrassed to commit this, but
it crashes (see situation in #5799) on my machine and I can't recreate
it outside this scenario. In any case I think as a general strategy we
should:

 1. Minimise reliance on msgbus
 2. Msgbus listeners themselves should be wary of invalid state (e.g. if
object is now unlinked)
 3. Not clear listeners (don't overreach)

src/bonsai/bonsai/bim/ifc.py

@@ -404,9 +404,6 @@ class IfcStore:
             obj.BIMStyleProperties.ifc_definition_id = 0
         else:  # bpy.types.Object
             obj.BIMObjectProperties.ifc_definition_id = 0
-        # NOTE: in theory this will also remove listeners added by other addons
-        # though never had a report when this would be a problem.
-        bpy.msgbus.clear_by_owner(obj)
 
     @staticmethod
     def execute_ifc_operator(operator: tool.Ifc.Operator, context: bpy.types.Context, is_invoke=False) -> set[str]: