doc: update minute-taking procedure for CTC

The doc says that the CTC moderator is responsible for taking minutes.

This change updates the doc to say that the moderator is responsible for
making sure that notes are taken, but not necessarily taking the notes
themselves.

PR-URL: https://github.com/nodejs/node/pull/9425


Reviewed-By: Josh Gavant <josh.gavant@outlook.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>