Fix Meetup exercise tests

[mk-mxp]

• Test with int as specified in students file stub.
• This requires adjusting the example solution to show it can still be done.
• Also remove superficial strict types file headers.

Follow-up of #592 (closed by creator)

[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.

If this PR does not affect the result of the test (or, for example, adds an edge case that is not worth rerunning all tests for), please add the following to the merge-commit message which will stops student's tests from re-running. Please copy-paste to avoid typos.

[no important files changed]

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[mk-mxp]

This change would invalidate a bunch of solutions, how can we prevent re-running tests for too old solutions? Or shouldn't we?

[homersimpsons]

This change would invalidate a bunch of solutions, how can we prevent re-running tests for too old solutions? Or shouldn't we?

I'm not sure how we should proceed about this, @ErikSchierboom do you have any suggestion?

As this aligns the type to the student file stub, to me we should proceed with this change. It's been 3y this stub is like this, so I wouldn't expect this to break too much student code.

This also aligns with the canonical-data.json from problem specifications.

[mk-mxp]

I just realized that this is the featured exercise for #48in24 week 32 and PHP will be one of the 3 languages of that week. So I decided to re-run all tests on community solutions to get as much "working code" there as possible.