meta: include a minimal CTC removal policy

Add language identifying a request for voluntary resignation as the
typical mechanism for addressing inactive CTC members.

PR-URL: https://github.com/nodejs/node/pull/7720


Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Shigeki Ohtsu <ohtsu@iij.ad.jp>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Julien Gilli <jgilli@nodejs.org>
Reviewed-By: James M Snell <jasnell@gmail.com>