Upgrade to a Cassandra version that works with Java 9

[snicoll]

See CASSANDRA-9608. Our sample is disabled on Java 9 at the moment.

See also jsevellec/cassandra-unit#249

[wilkinsona]

https://issues.apache.org/jira/browse/CASSANDRA-9608 has been fixed in Cassandra 4.0. We may want to consider switching from Cassandra Unit to Testcontainers in the smoke test.

[dreis2211]

Given that the smoke test was removed in ca1710e and we're on Cassandra 4+ I guess this can be closed.

[snicoll]

Indeed, the upgrade to Cassandra v4 was done as part of the upgrade to Spring Data Neumann, see #19588