Update README to clarify latest release version

[DavidXU12345]

Add note clarifying that latest release version may not include the most recent code changes and direct users to changelog for updates in different versions.

Is this a bug fix or adding new feature?
Minor update in README.

What is this PR about? / Why do we need it?
Add a note to remind users that the latest release version may not include the most recent code changes in master branch.

What testing is done?
N/A

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: DavidXU12345
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[k8s-ci-robot]

Hi @DavidXU12345. Thanks for your PR.

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