Update dubbo-samples-api to not use deprecated code

Currently those files are using deprecated call:
`AbstractInterfaceConfig::setApplication`.
Since those are examples that are used in `README.md` in dubbo project, it would be nice if they didn't show deprecated code, because it's also not trivial to understand why it's deprecated.
The code itself just uses `@Deprecated` without any comment whatsoever and there are no examples in `README.md` that show how that should look. The way I found it was by seeing this issue: https://github.com/apache/dubbo/issues/5679

After this gets updated here, I assume, the same has to be done in https://github.com/apache/dubbo in README.md, maybe in some other places too.

Now, this deprecated code is used all over dubbo-samples, but this submodule seems to be more important, as the code to it is shown as the first thing for people that try to learn and use the framework.