fix: require google-api-core 1.34.1

[parthea]

test: fix rest streaming fragment test
chore: update dependencies in requirements.txt

Fixes #1940 🦕

[parthea]

self = <google.api_core.rest_streaming.ResponseIterator object at 0x7ff861cdca50>

    def _grab(self):
        # Add extra quotes to make json.loads happy.
>       return self._response_message_cls.from_json(self._ready_objs.popleft())
E       AttributeError: from_json

This issue from the builld log was addressed in googleapis/python-api-core#604

[vchudnov-g]

Date!

[parthea]

This file was copied from https://github.com/googleapis/googleapis/blob/master/google/api/httpbody.proto which is why I kept the date. It's not clear if we should update the date when the file is copied from another repository.