Remove spring-boot-test dependency from OptaWeb Vehicle Routing

Using Spring Boot dependencies in a Quarkus project may be confusing. It's not a great example at the least.

Ideally, find a way to test Jackson de/serialization without using any dependencies, if it's not a lot of custom code. For ideas how to do that, see https://stackoverflow.com/questions/21787128/how-to-unit-test-jackson-jsonserializer-and-jsondeserializer.