Document incorrect results caution about Alluxio

[ebyhr]

TestHiveAlluxioMetastore.testGetPartitionsWithFilter always fails by incorrect results (#13252). We should document the behavior or (and) disable the integration by default and prepare a flag as @findepi mentioned in #13252 (comment)

Also, the Alluxio metastore integration seems not to be maintained well in the connector. If we don't recommend using it, it would be better to mention about that in this page

[findepi]

The test results suggest use of Alluxio integration may result in incorrect query results.
Since the integration with Alluxio is effectively unmaintained, and seems unused, I think we should remove it.

cc @apc999 @kokosing

[colebow]

Is it worth documenting in the meantime, or should I just wait for it to be removed?

[findepi]

@colebow please go ahead

[electrum]

Closing since Alluxio metastore is now gone.