Fix docstring example: session.begin_transaction() needs to be awaited (#807)
Fix docstring example: session.begin_transaction() needs to be awaited (#807)

Co-authored-by: Robsdedude <4b6b732ac8ff22b3b4135b4eb444224ec95646d7@neo4j.com>
neo4j/neo4j-python-driver,neo4j/neo4j-python-driver