zerorpc 0.6.3 is not compatible with pyzmq 23.0.0

significant changes were introduced in pyzmq 23.0.0

our tests are failing with
`AttributeError: module 'zerorpc.gevent_zmq' has no attribute 'PUSH'`

need to work with the zerorpc project to fix such errors.
check if we can modify our requirements so that we don't run with pyzmp >= 23.0.0 for now