Please add correct typing

In https://github.com/neo4j-labs/rdflib-neo4j/blob/master/rdflib_neo4j/Neo4jStore.py?plain=1#L21

Please change 
```python
def __init__(self, config: Neo4jStoreConfig, neo4j_driver: Driver = None):
```
to
```python
def __init__(self, config: Neo4jStoreConfig, neo4j_driver: Driver | None = None):
```