chore: update tests and docs to use MariaDB 2.x

[aaron-congo]

MariaDB 3.x should not be used against Aurora because it uses pipelining, which is not compatible with Aurora. This aligns with their documentation (see here). Additionally, these properties should also be set, because they also use pipelining.

Properties props = new Properties();
props.setProperty("usePipelineAuth", "false");
props.setProperty("useBatchMultiSend", "false");

This PR updates docs to clarify that MariaDB 2.x should be used with these properties. It also updates the tests to use MariaDB 2.x.

Relates to #1596

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.