vowpal-wabbit: fix `gcc-13` build failure
Without the change build fails on `master as
https://hydra.nixos.org/build/248985028:
In file included from /build/source/vowpalwabbit/core/src/named_labels.cc:5:
/build/source/vowpalwabbit/core/include/vw/core/named_labels.h:28:3: error: 'uint32_t' does not name a type
28 | uint32_t getK() const;
| ^~~~~~~~