[hotfix][docs] Fix typo and heading level in state backends documentation

[Dennis-Mircea]

What is the purpose of the change

This pull request fixes two small issues in the user-facing state backends documentation (docs/content/docs/ops/state/state_backends.md):

1. A typo in the heading ### Advanced RocksDB Memory Turning → ### Advanced RocksDB Memory Tuning. The body of the section uses "tuning" correctly, confirming the heading was a slip.
2. A heading-level inconsistency under ## Available State Backends: the sibling subsections ### The HashMapStateBackend and ### The EmbeddedRocksDBStateBackend are at level 3, but ## The ForStStateBackend was at level 2, implicitly closing the parent section. Demote it to ### The ForStStateBackend so it nests correctly under ## Available State Backends.

Brief change log

• docs/content/docs/ops/state/state_backends.md: rename the heading from Advanced RocksDB Memory Turning to Advanced RocksDB Memory Tuning.
• docs/content/docs/ops/state/state_backends.md: change ## The ForStStateBackend to ### The ForStStateBackend so it sits at the same nesting level as the other backend subsections. Hugo's heading slug is independent of level, so the existing anchor #the-forststatebackend (referenced from docs/{,.zh}/ops/state/disaggregated_state.md) continues to resolve.

The Chinese mirror under docs/content.zh/ does not carry the affected heading nor the ForStStateBackend subsection, so no parallel edits are needed there.

Verifying this change

This change is a trivial rework / code cleanup 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? not applicable

---

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

• Yes (please specify the tool below)

[flinkbot]

CI report:

• 10483c6 Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

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

[spuru9]

LGTM

[raminqaf]

LGTM!

[klion26]

LGTM, thanks!