Remove incubating from parquet-format release process

[asfimport]

Reporter: Ryan Blue / @rdblue
Assignee: Ryan Blue / @rdblue

Related issues:

• release parquet-format 2.3.1 (blocks)

PRs and other links:

• Format PR #34

_{Note: This issue was originally created as PARQUET-403. Please see the migration documentation for further details.}

[asfimport]

Ryan Blue / @rdblue:
Merged #34. Thanks for reviewing, Julien!