Sizzle: tweak for root selector shortcut. Fixes #12419.

diff --git a/src/sizzle b/src/sizzle
index 2f6e0fa245e8c2e767b31a0703687b60d1800954..15e840c84e5870fa3fd9e7f0163f5cf70f0c97ac 160000 (submodule)
--- a/src/sizzle
+++ b/src/sizzle
@@ -1 +1 @@
-Subproject commit 2f6e0fa245e8c2e767b31a0703687b60d1800954
+Subproject commit 15e840c84e5870fa3fd9e7f0163f5cf70f0c97ac