[FLINK-36595][docs] Explicitly set connector compatibility as string …

[hlteoh37]

…to prevent 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

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]

Thanks for opening this pull request! Please check out our contributing guidelines. (https://flink.apache.org/contributing/how-to-contribute.html)

[nicusX]

LGTM

[nicusX]

LGTM

[ferenc-csaky]

Hi! Thank you for your contribution. The CI fails because Flink 1.16 and 1.17 is not supported anymore and their download links are removed from the official download site. The release process for the v4.0 connector version supporting Flink 1.18 and 1.19 are already in progress, so would you mind reopen this change against v4.0 pls with the according versions?

[ferenc-csaky]

Closed, as it is obsolete now.