[FLINK-18385][docs-zh] Translate "DataGen SQL Connector" page into Chinese

[springMoon]

What is the purpose of the change

Translate "DataGen SQL Connector" page into Chinese.

The page url is https://ci.apache.org/projects/flink/flink-docs-master/zh/dev/table/connectors/datagen.html

The markdown file is located in flink/docs/dev/table/connectors/datagen.zh.md

Brief change log

• translate flink/docs/dev/table/connectors/datagen.zh.md.

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

[flinkbot]

Thanks a lot for your contribution to the Apache Flink project. I'm the @flinkbot. I help the community
to review your pull request. We will use this comment to track the progress of the review.

Automated Checks

Last check on commit 2e3e59a (Sun Jun 21 04:02:35 UTC 2020)

✅no warnings

_{Mention the bot in a comment to re-run the automated checks.}

Review Progress

• ❓ 1. The [description] looks good.
• ❓ 2. There is [consensus] that the contribution should go into to Flink.
• ❓ 3. Needs [attention] from.
• ❓ 4. The change fits into the overall [architecture].
• ❓ 5. Overall code [quality] is good.

Please see the Pull Request Review Guide for a full explanation of the review process.

Details

The Bot is tracking the review progress through labels. Labels are applied according to the order of the review items. For consensus, approval by a Flink committer of PMC member is required

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot approve description to approve one or more aspects (aspects: description, consensus, architecture and quality)
• @flinkbot approve all to approve all aspects
• @flinkbot approve-until architecture to approve everything until architecture
• @flinkbot attention @username1 [@username2 ..] to require somebody's attention
• @flinkbot disapprove architecture to remove an approval you gave earlier

[flinkbot]

CI report:

• 2e3e59a Azure: SUCCESS
• b915d61 Azure: PENDING

Bot commands

The @flinkbot bot supports the following commands:

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

[wuchong]

Suggested change

	<td>生成器的 '#' 字段。可以是 'sequence' 或 'random'。</td>
	<td>指定 '#' 字段的生成器。可以是 'sequence' 或 'random'。</td>

[wuchong]

Suggested change

	表的有界性：表中字段的数据生成完成后，就读取完成。 因此，表的有界性取决于字段的有界性。
	表的有界性：当表中字段的数据全部生成完成后，source 就结束了。 因此，表的有界性取决于字段的有界性。

[wuchong]

Thanks for the contribution @springMoon . Will merge this.