Remove errant in arcanist.php
Summary: This causes 49 to be printed out preceding the start of my next terminal line every time there is an exception thrown.
Test Plan: did not see 49 printed out when exceptions were thrown
Reviewers: Blessed Reviewers, epriestley
Reviewed By: Blessed Reviewers, epriestley
Differential Revision: https://secure.phabricator.com/D14030