[FLINK-32175] [docs-zh] translate doc(datagen.md) into chinese

[niliushall]

jira: https://issues.apache.org/jira/browse/FLINK-32175

(The sections below can be removed for hotfixes of typos) -->

What is the purpose of the change

• translate doc(datagen.md) into chinese

Brief change log

• translate doc(datagen.md) into chinese

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

[flinkbot]

CI report:

• b7d7050bb3118bd2a64abbc760dd9666fd4f75bd Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

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

[niliushall]

@roncohen @is Can you help review this PR in your free time? Thanks.