buffer: shorten deprecation warning

Shorten the deprecation warning for Buffer constructor.

PR-URL: https://github.com/nodejs/node/pull/19741


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>