build: make 'floating patch' message informational

Downgrade the 'Using floating patch' message that is emitted when a local patch is applied to the bundled ICU from a warning to a notice. There isn't anything the user can or should do so warning isn't appropriate. Instead of angry yellow use soothing green.

Fixes: https://github.com/nodejs/node/issues/26346 CI: https://ci.nodejs.org/job/node-test-pull-request/21030/