[Docs][Java] Some Java docs are on both repositories

[raulcd]

Describe the enhancement requested

It seems we have some duplicated documentation on the repositories. On the apache/arrow:
https://github.com/apache/arrow/tree/57f626189326251c8144d4fad89c28220c68ca75/docs/source/java
on apache/arrow-java:
https://github.com/apache/arrow-java/tree/ed81e5981a2bee40584b3a411ed755cb4cc5b91f/docs/source

For JS we added the following stub page:
https://github.com/apache/arrow/tree/57f626189326251c8144d4fad89c28220c68ca75/docs/source/js

We probably should do the same for Java docs on the apache/arrow repository

Component(s)

Documentation, Java