Fix sprintf buffer leaks on 32-bit systems

As qsizetype is [guaranteed to be the same size as size_t][1],
%6zx seems like the more appropriate option for it here.

[1]: https://doc.qt.io/qt-6/qttypes.html#qsizetype-typedef



Co-authored-by: Tasos Sahanidis <tasos@tasossah.com>