Java JDBC: Use explicit schema name `testdrive`

[amotl]

Otherwise, resources would be created within the crate schema, which might be unfortunate for various reasons.

The intention of the micro examples is to show users best practices. While the documentation will certainly educate about the doc schema, I think it will be fine to use a canonical dedicated schema name for this collection of example programs?

• See also: https://github.com/crate/crate-clients-tools/pull/151