[FLINK-36422][docs] Fix PyFlink jar download link

[z3d1k]

What is the purpose of the change

Fix PyFlink jar download link.

Brief change log

• Use py_connector_download_link shortcode to generate link with correct connector artifact version, instead of Flink version.

Verifying this change

• Generated documentation locally

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, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

[boring-cyborg]

Thanks for opening this pull request! Please check out our contributing guidelines. (https://flink.apache.org/contributing/how-to-contribute.html)

[boring-cyborg]

Awesome work, congrats on your first merged pull request!