Revert QUnit to a stable release (v1.6.0)

diff --git a/test/qunit b/test/qunit
index f08dc894391c856fc9cfe715ec2198fab9af60d9..3f5e8b2123c66d4c9ab83b76f3785e799cd9b5d5 160000 (submodule)
--- a/test/qunit
+++ b/test/qunit
@@ -1 +1 @@
-Subproject commit f08dc894391c856fc9cfe715ec2198fab9af60d9
+Subproject commit 3f5e8b2123c66d4c9ab83b76f3785e799cd9b5d5