ToastQueue: use strings for data instead of views.

Why the fuck didn't I catch that sooner ?

src/ToastQueue/ToastQueue.h

@@ -62,7 +62,7 @@ class Toast {
 
     private:
         Type _type{Type::Default};
-        Containers::StringView _message;
+        Containers::String _message;
         std::chrono::milliseconds _timeout;
         std::chrono::steady_clock::time_point _creationTime;
         Animation::Track<UnsignedInt, Phase> _phaseTrack;