Change documentation for unit-allowed-list ignoreFunctions option

[mattxwang]

Which issue, if any, is this issue related to?

None, as it's a documentation fix.

Is there anything in the PR that needs further explanation?

Motivated from discussion for ignoreFunctions in unit-disallowed-list.

I'm not sure how to best title this PR (tried to base it off of the CHANGELOG groups in the maintainer guide), feel free to re-title with a better wording!

[changeset-bot]

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Latest commit: d5969b5

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[ybiquitous]

Thank you. LGTM 👍🏼