deps: fix sign-compare warning in ncrypto
Fix following warning in GN build:
../../node/deps/ncrypto/ncrypto.cc:1197:12: error: comparison of integers of different signs: 'int' and 'size_t' (aka 'unsigned long') [-Werror,-Wsign-compare]
1197 | if (size < dp.size()) {
| ~~~~ ^ ~~~~~~~~~