CHEF-6434 Update server platforms in docs

[IanMadd]

Description

Remove:

• Centos 8 (EOL)
• Ubuntu 16 and 18 (EOL)

Add:

• Amazon 2023
• Rocky Linux 9

Related PRs / Issues

#3720 #3732

CHEF-10296 CHEF-6434

Issues Resolved

[List any existing issues this PR resolves, or any Discourse or StackOverflow discussions that are relevant]

Check List

• [ ] New functionality includes tests
• [ ] All buildkite tests pass
• [ ] Full omnibus build and tests in buildkite pass
• [ ] All commits have been signed-off for the Developer Certificate of Origin. See https://github.com/chef/chef/blob/main/CONTRIBUTING.md#developer-certification-of-origin-dco
• [ ] PR title is a worthy inclusion in the CHANGELOG

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Quality Gate passed

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