src: use `%zx` in printf for size_t

This fixes a compiler warning on Windows.

PR-URL: https://github.com/nodejs/node/pull/21323


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>
Reviewed-By: Bartosz Sosnowski <bartosz@janeasystems.com>