[hotfix][build] Release branch should use SNAPSHOT version

[leonardBang]

Purpose of the change

hotfix: fix version in release branch

Verifying this change

Please make sure both new and modified tests in this PR follows the conventions defined in our code quality
guide: https://flink.apache.org/contributing/code-style-and-quality-common.html#testing

(Please pick either of the following options)

This change is already covered by existing tests, such as (please describe tests).

(yes)

Significant changes

(Please check any boxes [x] if the answer is "yes". You can first publish the PR and check them afterwards, for
convenience.)

• Dependencies have been added or upgraded
• Public API has been changed (Public API is any class annotated with @Public(Evolving))
• Serializers have been changed
• New feature has been introduced
  • If yes, how is this documented? (not applicable / docs / JavaDocs / not documented)

[boring-cyborg]

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[leonardBang]

CI passed, merging...