coloreditor: Don't unref unless we own it

Calling gtk_widget_class_bind_template_child does
*not* give you a reference that you need to unref.
It manages the reference for you. So calling
g_clear_object on such a member is wrong.

gtk/gtkcoloreditor.c

@@ -447,9 +447,6 @@ gtk_color_editor_dispose (GObject *object)
 
   dismiss_current_popup (editor);
   g_clear_object (&editor->picker);
-  g_clear_object (&editor->h_adj);
-  g_clear_object (&editor->s_adj);
-  g_clear_object (&editor->v_adj);
 
   G_OBJECT_CLASS (gtk_color_editor_parent_class)->dispose (object);
 }