LibWeb: Do not return a GC::Root from HTMLTrackElement's track getter

There's no need to create a root each time the getter is called. We
should also allocate it in the `initialize` overload rather than the
constructor.

Libraries/LibWeb/HTML/HTMLTrackElement.h

@@ -21,7 +21,7 @@ public:
 
     WebIDL::UnsignedShort ready_state();
 
-    GC::Root<TextTrack> track() { return m_track; }
+    GC::Ref<TextTrack> track() { return *m_track; }
 
 private:
     HTMLTrackElement(DOM::Document&, DOM::QualifiedName);