[Addon] fix: removing hardcoded non-existing flink operator helm chart, and allowing for parameterising operator version

[kujon]

Hello Everyone 👋 Flink people seem to have removed old versions of the operator from their helm chart repository. The oldest version that is still in existence is 1.7.0. I've removed the hardcoded version reference, and allowed for parameterising the version going forward.

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• Update addon should modify the version in metadata.yaml to generate a new version.

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