csl: Add fileOwner for CHANGELOG.rst
csl: Add fileOwner for CHANGELOG.rst

Problem/Solution:

Add the whole team as the file owner for the CHANGELOG.rst file for: finagle,
finatra, scrooge, twitter-server, util

Differential Revision: https://phabricator.twitter.biz/D886420

twitter/finatra,twitter/finatra,twitter/finatra