[FLINK-34250][docs] add new option for avro format docs

[HuangZhenQiu]

What is the purpose of the change

Add the missing new Avro option in corresponding doc.

Brief change log

• Add new option in avro.md

Verifying this change

This change is a trivial doc change without any test coverage.

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? (docs)

[flinkbot]

CI report:

• 2328332 Azure: SUCCESS

Bot commands

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[PatrickRen]

@HuangZhenQiu Thanks for the patch! LGTM.

Could you also add this option to the Chinese doc at docs/content.zh/docs/connectors/table/formats/avro.md?

[HuangZhenQiu]

@HuangZhenQiu Thanks for the patch! LGTM.

Could you also add this option to the Chinese doc at docs/content.zh/docs/connectors/table/formats/avro.md?

Thanks for pointing it out. Updated accordingly.

[PatrickRen]

@HuangZhenQiu Thanks for the update! LGTM