[hotfix][docs] Fix incorrect HashMapStateBackend recommendations

[Dennis-Mircea]

What is the purpose of the change

This pull request fixes incorrect recommendations in the State Backends documentation. The "encouraged for" bullets under the HashMapStateBackend section were copy-pasted from the EmbeddedRocksDBStateBackend section and incorrectly recommended the heap-based backend for "jobs with large state, long windows, large key/value states" and "all high-availability setups", which is the opposite of HashMapStateBackend's actual sweet spot. The fix replaces them with bullets that reflect HashMapStateBackend's real strengths (in-memory access for state that fits on the JVM heap, avoiding (de-)serialization on every state access). Both the English and Chinese versions of the page are updated to stay in sync.

Brief change log

• Replaced the misleading bullets under "The HashMapStateBackend is encouraged for:" in docs/content/docs/ops/state/state_backends.md.
• Mirrored the same fix in the Chinese translation at docs/content.zh/docs/ops/state/state_backends.md.

Verifying this change

This change is a trivial documentation fix without any test coverage. It can be verified by rendering the docs locally (docs/build_docs.sh) and inspecting the "The HashMapStateBackend" section on both the English and Chinese pages.

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

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CI report:

• bdfa1cc Azure: SUCCESS

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[spuru9]

LGTM