Update parquet-format pin

[alamb]

Rationale

There have been a few changes to the parquet-format repo that would be nice to reflect on the https://parquet.apache.org/ website

For example:

• GH-561: variant schema examples to use (VARIANT(1)) parquet-format#562
• Correct VARIANT Logical Type annotation in Parquet examples parquet-format#555

Changes:

1. Update pin to parquet-format

[wgtmac]

Thank you, @alamb!