[hotfix][docs] Explicitly set connector compatibility as string to pr…

[hlteoh37]

…event version comparison mismatch

Purpose of the change

• Set version as string to prevent version comparison mismatch. Issue has happened for other connectors too : [FLINK-36595][docs] Explicitly set connector compatibility as string to prevent version comparison mismatch flink-connector-kafka#132

Verifying this change

After fix, the version artifact shows up.

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)