say: Sync with problem specifications

[tasxatzial]

Also closes #302, as the 'extensions' section mentioned in #302 no longer exists in the synced version.

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[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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[michalporeba]

This change will potentially make some solutions to fail, so they should be regenrated, but at the same time we should merge it to conform to the problem specification.