Follow up improvements to verification guide for `parquet-java` release

Follow up to https://github.com/apache/parquet-site/pull/98

> We can also take some inspiration from https://iceberg.apache.org/how-to-release/#how-to-verify-a-release

_Originally posted by @kevinjqliu in https://github.com/apache/parquet-site/pull/98#pullrequestreview-4757651125_

Start by reading the referenced parquet-site pull request 98 and the Iceberg release-verification guide. Compare their verification guidance and determine which follow-up improvements are intended for the parquet-java release guide; done means those agreed improvements are documented, though this issue does not specify the target file or exact changes.

Written by the indexing model from the issue text.