Upgrade merge script to run on python3

It looks like the the parquet-java merge script is setup to run only on python2 which is EOL.  We should update it to run on python3 I plan to do this at least minimally without the Jira integration.

**Reporter**: [Micah Kornfield](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=emkornfield) / @emkornfield
**Assignee**: [Micah Kornfield](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=emkornfield) / @emkornfield
#### PRs and other links:
- [GitHub Pull Request #1373](https://github.com/apache/parquet-java/pull/1373)

_{**Note**: *This issue was originally created as [PARQUET-2495](https://issues.apache.org/jira/browse/PARQUET-2495). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

Inizia esaminando il parquet-java merge script e il GitHub pull request #1373 collegato. Verifica le ipotesi esistenti su Python 2 e l’ambito indicato nell’issue, quindi verifica che lo script venga eseguito con Python 3 senza l’integrazione Jira.

Scritto dal modello di indicizzazione a partire dal testo della issue.