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GH-43217: [Java] Remove flight-core shaded jars (#43224)

### Rationale for this change

Remove extra jars generated by `flight-core` modules:
- they do not seem to be used by the project internally and does not seem to satisfy some external purpose as well
- they are not compatible with JPMS

### Are these changes tested?

CI/CD

### Are there any user-facing changes?

Several extras jars attached to `org.apache.arrow:flight-core` artifact will stop being published to Apache Maven Repository/Maven Central.
* GitHub Issue: #43217

Authored-by: Laurent Goujon <laurent@apache.org>
Signed-off-by: Dane Pitkin <dpitkin@apache.org>