src: remove ref to tools/generate_code_cache.js

This commit removes the reference to tools/generate_code_cache.js
and replaces it with a note about more information being available
in tools/code_cache/README.md.

PR-URL: https://github.com/nodejs/node/pull/33825


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: David Carlier <devnexen@gmail.com>