Update Neo4j generators for new batch_num argument (#1050)
Update Neo4j generators for new batch_num argument (#1050)

In 4070ccf24d67802a08a9f70ca3e7567a0a53a7fc (#844), a second argument
(`batch_num`) was added to the `sample_features` function in the
`BatchedNodeGenerator` class, and most subclasses were updated, but not the
Neo4j ones. This PR adds that argument.

This code is untested on CI (even the notebooks #849), but that's being worked
on (#1046), and I've manually verified the notebooks run for now.

See: #1016

stellargraph/stellargraph,stellargraph/stellargraph