docs: clarify enforce vs hook.order

[wmertens]

Description

Just a small bit of documentation to clarify the role of order vs enforce.

Additional context

I was confused about this, would have prevented #16173

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What is the purpose of this pull request?

• Documentation update

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• Read the Contributing Guidelines, especially the Pull Request Guidelines.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Update the corresponding documentation if needed.

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