[FLINK-36173][docs] Fix invalid link in checkpoint documentation

[gaborgsomogyi]

What is the purpose of the change

Some of the places we still have checkpointing-with-parts-of-the-graph-finished-beta link instead of checkpointing-with-parts-of-the-graph-finished which doesn't lead anywhere. In this PR I've fixed it.

Brief change log

Fixed checkpointing-with-parts-of-the-graph-finished link in checkpoint documentation.

Verifying this change

• docker run -v $(pwd):/src -p 1313:1313 jakejarvis/hugo-extended:latest server --buildDrafts --buildFuture --bind 0.0.0.0
• Manually visited locally generated page

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

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable