Add missing test for low-level full mana requirement Role Playing Game

[lennnerd]

The problem description states: If they player's level is below 10, their mana should be None. One of the top results did not implement this requirement due to a missing test.

This PR modifies a test verifying that low level players get their mana set to None.

@Reviewer: If preferred, i can also add a new test instead modifying the current test.

[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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[no important files changed]

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[lpil]

Perhaps removing that requirement would be best. It's less disruptive and it doesn't teach anything in particular.

[lennnerd]

Fair point.

Personally, as a beginner I quite liked the aspect of trying to reduce nesting with the extra mana requirement. But the less disruptive change is changing the docs. Its your call. I adapted the PR.

[lpil]

Thank you! 💜