[docs] Replaced outdated 'RocksDBStateBackend.setOptions(..)'

[XComp]

…by RocksDBStateBackend.setRocksDBOptions(..)' and fixed typo in parameter list (PptionsFactory -> RocksDBOptionsFactory).

What is the purpose of the change

This was a doc fix requested by @NicoK .

Brief change log

The outdated field RocksDBStateBackend.setOptions(..) was replaced by RocksDBStateBackend.setRocksDBOptions(..).
As part of this change, another typo got fixed: PptionsFactory -> RocksDBOptionsFactory

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/Mesos, 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? no

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Last check on commit 9fc9a71 (Tue Aug 18 06:38:05 UTC 2020)

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[tillrohrmann]

Thanks for creating this PR @XComp. LGTM. Merging this PR now.