Remove the Rc from ROOTED_TRACEABLES.

It does not appear to be necessary.
servo · bors-servo · Dec 14, 2016 · Dec 13, 2016 · Dec 13, 2016 · 061350ed7d271adfe03d87d1865ca2f3721ec3d3
commit 061350ed7d271adfe03d87d1865ca2f3721ec3d3
diff --git a/components/script/dom/bindings/trace.rs b/components/script/dom/bindings/trace.rs
@@ -574,8 +574,8 @@ pub struct RootedTraceableSet {
 
 thread_local!(
     /// TLV Holds a set of JSTraceables that need to be rooted
-    static ROOTED_TRACEABLES: Rc<RefCell<RootedTraceableSet>> =
-        Rc::new(RefCell::new(RootedTraceableSet::new()));
+    static ROOTED_TRACEABLES: RefCell<RootedTraceableSet> =
+        RefCell::new(RootedTraceableSet::new());
 );
 
 impl RootedTraceableSet {