Rock Paper Scissors: Fix ambiguous parameter

[sukairaida]

Because

The third instruction on the step 5 of the RPS project refers to a humanSelection parameter that hasn't been defined yet, this PR replaces it with humanChoice which is the given name to the parameter in the fuction defined before. This could prevent new learners from getting confused about it.

This PR

• Replace humanSelection with humanChoice on the third instruction of the 5th step of the project.

Issue

Closes #27988

Additional Information

Pull Request Requirements

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[MaoShizhong]

Many thanks!