chore: use "Maintenance" instead of "Internal" in changelog

[Josh-Cena]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

Following discussions on Discord, we agreed to rename "Internal" to "Maintenance", and reserve "Internal" for those tags that will not be added to the changelog.

[netlify]

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