Update test cases

Grab what you want, mark it and make a PR. These exercises need updates:

- [ ] grade school (@Elahi-cs )
- [x] matching-brackets (@sz245 )
- [x] protein-translation (@vaeng) #912
- [ ] high-scores (@vaeng) #911
- [x] pangram (@BNAndras) #848
- [x] isogram (@BNAndras) #849
- [x] allergies (@vaeng) #817
- [x] anagram (@CadeMichael) #784
- [x] armstrong-numbers (@ahans) #808
- [x] bank-account (@KevDi) #826
- [x] complex-numbers (@KevDi) #829
- [x] crypto-square (@ahans) #827
- [x] gigasecond (@ahans) #810
- [x] hamming (@ahans) #775 #789
- [x] luhn (@vaeng) #818
- [x] perfect-numbers (@vaeng) #819
- [x] phone-number (@tanno1 ) #870
- [x] prime-factors (@JagritGumber ) #895
- [x] say (@Elahi-cs ) #903
- [x] triangle (@DebbieSan) #787
- [x] word-count (@vaeng) #820

I made a [wiki entry on test case updates](https://github.com/exercism/cpp/wiki/Test-Cases-for-Practice-Exercises) if you are unsure how to start.