Backport of docs: fixup note about node scope for admin partitions into release/1.13.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #17147 to be assessed for backporting due to the inclusion of the label backport/1.13.

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The below text is copied from the body of the original PR.

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Description

Fixup an inaccurate note about nodes being scoped to namespaces.

Testing & Reproduction steps

Links

PR Checklist

• updated test coverage
• external facing docs updated
• appropriate backport labels added
• not a security concern

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Overview of commits

• aaf63f6

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[github-team-consul-core-pr-approver]

Auto approved Consul Bot automated PR