R1:62a27c1caa9c

Fix uri.allowed-protocols default value

Summary: Fixes T2392.

Test Plan: grepped for others, this is the only `set` with non-array default

Reviewers: chad, starruler

Reviewed By: starruler

CC: aran

Maniphest Tasks: T2392

Differential Revision: https://secure.phabricator.com/D4611