[FLINK-29458][docs] When two tables have the same field, do not speci…

[ZmmBigdata]

What is the purpose of the change

When two tables have the same field, do not specify the table name,Exception will be thrown：SqlValidatorException :Column 'currency' is ambiguous.

The page url is https://nightlies.apache.org/flink/flink-docs-release-1.14/docs/dev/table/sql/queries/joins/

Brief change log

The table name is added before the query field，“ orders.currency”

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? no

[flinkbot]

CI report:

• 9d25c8e Azure: SUCCESS
• 84e8d4b Azure: PENDING

Bot commands

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

[lincoln-lil]

@ZmmBigdata Thanks for fixing this! It's better to fix the chinese version (though it hasn't been translated yet) docs/content.zh/docs/dev/table/sql/queries/joins.md as well.

[ZmmBigdata]

@ZmmBigdata Thanks for fixing this! It's better to fix the chinese version (though it hasn't been translated yet) docs/content.zh/docs/dev/table/sql/queries/joins.md as well.

@lincoln-lil Can you merge this first? I'll change the Chinese document，I want a contributor，hhh

[wuchong]

LGTM.