Fix: Moved tests section to bottom of package.yaml to avoid issues with test-runner code injection

[cdimitroulas]

The new test runner (https://github.com/exercism/haskell-test-runner/pull/104) expects the tests section of package.yaml to be the last one and the dependencies list to be the bottom as it simply appends new dependencies to the bottom of the file using code injection.

This change ensures that this exercise will work correctly with the latest changes of the test runner.

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