csl: Removed coursier to fix the build
csl: Removed coursier to fix the build

Summary: Problem

There seems to be a bug with sbt 1.0.x, sbt-pgp, and coursier.
See https://github.com/coursier/coursier/issues/694

Solution

Stop using coursier to unblock publishing.

JIRA Issues: CSL-5520

Differential Revision: https://phabricator.twitter.biz/D112092

twitter/twitter-server,twitter/twitter-server,twitter/twitter-server