exercises(queen-attack): remove input validation tests

[ee7]

Remove QueenError and the input validation tests. They weren't interesting - there's no good reason for init params to be i8 when the valid range is between 0 and 7 inclusive.

This PR will break everybody's solution, but I think that's worthwhile.

Closes: #223 Refs: #229

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To-do:

• [ ] Check whether we should add an .append file that explains how to assert