doc: simplify ccache instructions

`ccache` has reasonable defaults for `max_size` and `cache_dir` so
remove instructions to set those things explicitly.

Change fenced code from `console` to `bash` for easier copy/paste.

PR-URL: https://github.com/nodejs/node/pull/40550
Fixes: https://github.com/nodejs/node/issues/40542


Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>