SceneRefract: Fix potential memory leak

The memory leak occurs when using the scene for multiple benchmarks.
diff --git a/src/scene-refract.cpp b/src/scene-refract.cpp
index b936362..db0aec8 100644
--- a/src/scene-refract.cpp
+++ b/src/scene-refract.cpp
@@ -87,11 +87,6 @@
                                            "false,true");
 }
 
-SceneRefract::~SceneRefract()
-{
-    delete priv_;
-}
-
 bool
 SceneRefract::supported(bool show_errors)
 {
@@ -150,6 +145,7 @@
 {
     // Add scene-specific teardown here
     priv_->teardown();
+    delete priv_;
     Scene::teardown();
 }
 
diff --git a/src/scene.h b/src/scene.h
index 88f839d..66377e1 100644
--- a/src/scene.h
+++ b/src/scene.h
@@ -580,7 +580,6 @@
     RefractPrivate* priv_;
 public:
     SceneRefract(Canvas& canvas);
-    ~SceneRefract();
     bool supported(bool show_errors);
     bool load();
     void unload();