Leave the implicit uint to int cast

Leave the implicit uint to int cast

I wrongly (and stupidly) assumed the int in QBitArray was treated as a
hash as well but it is an index so it must be positive. Also to make
things even worse I misread on which expression clang-tidy was
complaining regarding the implementation specific narrowing
conversion... This is happening after the modulo operator and not
before. We're in a safe range of values at that point, so it's fine to
let the narrowing happen.

Signed-off-by: Kevin Ottens <kevin.ottens@nextcloud.com>