[hotfix][doc] Add flink-s3-fs-native in AGENTS.md

[Samrat002]

What is the purpose of the change

Update AGENTS.md to add flink-s3-fs-native.

Verifying this change

N/A

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

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

Documentation

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

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Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)

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CI report:

• 31de676 Azure: SUCCESS

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