Revert "clutter: Mark BinLayout as final"

This reverts commit 2dca60bd1c.

As GNOME Shell subclass that layout manager 3 times in the JS code part

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3509>

clutter/clutter/clutter-bin-layout.c

@@ -54,14 +54,9 @@
 #include "clutter/clutter-layout-meta.h"
 #include "clutter/clutter-private.h"
 
-struct _ClutterBinLayout
-{
-  ClutterLayoutManager parent_instance;
-};
-
-G_DEFINE_FINAL_TYPE (ClutterBinLayout,
-                     clutter_bin_layout,
-                     CLUTTER_TYPE_LAYOUT_MANAGER)
+G_DEFINE_TYPE (ClutterBinLayout,
+               clutter_bin_layout,
+               CLUTTER_TYPE_LAYOUT_MANAGER)
 
 static void
 clutter_bin_layout_get_preferred_width (ClutterLayoutManager *manager,

clutter/clutter/clutter-bin-layout.h

@@ -35,11 +35,23 @@ G_BEGIN_DECLS
 #define CLUTTER_TYPE_BIN_LAYOUT (clutter_bin_layout_get_type ())
 
 CLUTTER_EXPORT
-G_DECLARE_FINAL_TYPE (ClutterBinLayout,
-                      clutter_bin_layout,
-                      CLUTTER,
-                      CIN_LAYOUT,
-                      ClutterLayoutManager)
+G_DECLARE_DERIVABLE_TYPE (ClutterBinLayout,
+                          clutter_bin_layout,
+                          CLUTTER,
+                          BIN_LAYOUT,
+                          ClutterLayoutManager)
+
+/**
+ * ClutterBinLayoutClass:
+ *
+ * The #ClutterBinLayoutClass structure contains only private
+ * data and should be accessed using the provided API
+ */
+struct _ClutterBinLayoutClass
+{
+  /*< private >*/
+  ClutterLayoutManagerClass parent_class;
+};
 
 CLUTTER_EXPORT
 ClutterLayoutManager *  clutter_bin_layout_new  (void);