Updating SNAT variable documentation

[jaydeokar]

What type of PR is this?
documentation

Which issue does this PR fix?: N/A

What does this PR do / Why do we need it?:
N/A

Testing done on this change: N/A

Will this PR introduce any new dependencies?: N/A

Will this break upgrades or downgrades? Has updating a running cluster been tested?:
N/A

Does this change require updates to the CNI daemonset config files to work?: N/A

Does this PR introduce any user-facing change?: N/A

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[Copilot]

Pull Request Overview

This PR updates documentation for the SNAT configuration variable in the VPC CNI README. The changes focus on clarifying when and why to disable SNAT in Kubernetes networking configurations.

• Removes outdated Kubernetes version compatibility entries from the support matrix
• Rewrites SNAT variable documentation for improved clarity and conciseness

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