Remove openstack-python3 from accessbot
The channel has been retired, and is currently set to private and
forwarding everyone to #openstack-dev.  We don't need accessbot to
manage it any more.
@@ -241,7 +241,6 @@ channels:
- name: openstack-product
- name: openstack-ptg
- name: openstack-publiccloud
- - name: openstack-python3
- name: openstack-qa
- name: openstack-qinling
- name: openstack-quota
