src: fix warning in cares_wrap.cc

This commit fixes the following warning:

./src/cares_wrap.cc:1268:5: warning: comparison of integers of
    different signs: 'uint32_t' (aka 'unsigned int') and 'int'
    [-Wsign-compare]
    CHECK_EQ(ret->Length(), a_count + aaaa_count);

PR-URL: https://github.com/nodejs/node/pull/25230


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>