Updated TAGGING.md to mention minimum version for tagging

[rdpsin]

Is this a bug fix or adding new feature?
Doc fix.

What is this PR about? / Why do we need it?
Updates TAGGING.md to mention that tagging support will be available from v1.6.0 onwards.
(Note: as of this PR, v1.6.0 doesn't yet exist).

What testing is done?

[k8s-ci-robot]

Hi @rdpsin. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[gtxu]

/ok-to-test

[gtxu]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gtxu, rdpsin

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