Remove deprecated code from MLLP component

There are some configuration options and some static variables that have been marked as deprecated in camel-mllp since Camel 2.x. I think it's time to remove them.

The deprecated static DEFAULT_CHARSET variable in MllpEndpoint actually breaks the mllp endpoint charset resolution in Quarkus native mode, since the default ends up being set at build time and it is then not possible to override at runtime.