[FLINK-34001][docs][table] Fix ambiguous document description towards the default value for configuring operator-level state TTL

[LadyForest]

What is the purpose of the change

This is a trivial PR to eliminate the ambiguous description about the meaning of 0ms when configuring operator-level state TTL for SQL/TableAPI using compiled plan.

Brief change log

Change "state retention is not enabled" to "state never expires"

Verifying this change

This change is a trivial rework without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes / no)
• The serializers: (yes / no / don't know)
• The runtime per-record code paths (performance sensitive): (yes / no / don't know)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (yes / no / don't know)
• The S3 file system connector: (yes / no / don't know)

Documentation

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

[xuyangzhong]

LGTM

[flinkbot]

CI report:

• b43913d Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build

[LadyForest]

The CI failure is not relevant to the changes

[LadyForest]

@flinkbot run azure

[LadyForest]

The CI failure is caused by FLINK-34012