sync diamond

[tomasnorre]

Resolves #826

[github-actions]

This PR touches files which potentially affect the outcome of the tests of an exercise. This will cause all students' solutions to affected exercises to be re-tested.

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[tomasnorre]

This is not completely done, as I wasn't aware how to deal with the change of function diamond() to rows() according to the https://github.com/exercism/problem-specifications/blob/main/exercises/diamond/canonical-data.json

[mk-mxp]

Thanks for this!