Remove unused ba and br in RegStateRecord state fn

[kentbull]

I was getting an error when reloading a registry after a cold-start KERIA as the following error message shows. Removing ba and br from the vdr.eventing.state function resolved things for me.

Error

2024-02-03 12:27:01 [FALCON] [ERROR] GET /identifiers/{my_aid}/registries => Traceback (most recent call last):
  File "falcon/app.py", line 365, in falcon.app.App.__call__
  File "/path/to/keria/src/keria/app/credentialing.py", line 92, in on_get
    state=asdict(registry.tever.state())
                 ^^^^^^^^^^^^^^^^^^^^^^
  File "/path/to/keripy/src/keri/vdr/eventing.py", line 800, in state
    br = self.cuts
         ^^^^^^^^^
AttributeError: 'Tever' object has no attribute 'cuts'