[FLINK-14557][python] Cleanup the py4j package

[dianfu]

What is the purpose of the change

This pull request clean up the py4j package by removing the unused directory __MACOSX

Brief change log

• Clean up the py4j package by removing the unused directory __MACOSX

Verifying this change

This change is a trivial rework without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (no)
• The serializers: (no)
• The runtime per-record code paths (performance sensitive): (no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: (no)
• The S3 file system connector: (no)

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not applicable)

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Automated Checks

Last check on commit cb60e4d (Wed Dec 04 14:54:18 UTC 2019)

Warnings:

• No documentation files were touched! Remember to keep the Flink docs up to date!

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Review Progress

• ❓ 1. The [description] looks good.
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• ❓ 3. Needs [attention] from.
• ❓ 4. The change fits into the overall [architecture].
• ❓ 5. Overall code [quality] is good.

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CI report:

• cb60e4d : SUCCESS Build

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