docs: update readme to remove cassandra-only setup (#228)

Cassandra-only setup has been removed since v1.21

Author: mrsimonemms

README.md

@@ -63,7 +63,6 @@ Here is a list of available files and the dependencies they use.
 | docker-compose.yml                     | PostgreSQL and Elasticsearch (default)                        |
 | docker-compose-tls.yml                 | PostgreSQL and Elasticsearch with TLS                         |
 | docker-compose-postgres.yml            | PostgreSQL                                                    |
-| docker-compose-cass.yml                | Cassandra                                                     |
 | docker-compose-cass-es.yml             | Cassandra and Elasticsearch                                   |
 | docker-compose-mysql.yml               | MySQL                                                         |
 | docker-compose-mysql-es.yml            | MySQL and Elasticsearch                                       |