armstrong-numbers: Inaccurate test/description

The armstrong-numbers description of `There are no 2 digit Armstrong numbers` and the test data of `10` don't quite line up. The tests would happily pass if `11` was detected as an armstrong number even though it would be incorrect.

https://github.com/exercism/problem-specifications/blob/ca9c09eda445e642317a043bf9c949fbffae4020/exercises/armstrong-numbers/canonical-data.json#L14-L20

I would suggest that the ideal solution is to actually have tests that assert on the entire range of 2 digit numbers to make the tests accurate to the description, although the simplest possible thing might be just adjusting the description to be more specific to the test case. `Two digit number that is not an Armstrong number`