deps: restore minimum ICU version to 68

Refs: https://github.com/v8/v8/commit/edac49681843447cc483b164a26d00755870b08c

PR-URL: https://github.com/nodejs/node/pull/39470


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Beth Griggs <bgriggs@redhat.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>