Create index for change set relationship

[fbiville]

This is only available starting with Neo4j 4.3 (see https://neo4j.com/docs/cypher-manual/current/indexes-for-search-performance/#administration-indexes-create-a-single-property-index-for-relationships).

This would be useful for the IN_CHANGELOG relationship between the __LiquibaseChangeLog node and __LiquibaseChangeSet. The indexed relationship properties should be orderExecuted and dateExecuted.