cogl-object: remove un-used cogl_object_get_type

A non-static function named cogl_object_get_type was inadvertently added
during the addition of the CoglObject base type, but there is no public
prototype in the headers and it's only referenced inside cogl-object.c
to implement cogl_handle_get_type() for compatibility. This removes the
function since we don't want to commit to CoglObject always simply being
a boxed type. In the future we may want to register hierarchical
GTypeInstance based types.

cogl/cogl-object.c

@@ -103,7 +103,7 @@ cogl_handle_unref (CoglHandle handle)
 }
 
 GType
-cogl_object_get_type (void)
+cogl_handle_get_type (void)
 {
   static GType our_type = 0;
 
@@ -117,12 +117,6 @@ cogl_object_get_type (void)
   return our_type;
 }
 
-GType
-cogl_handle_get_type (void)
-{
-  return cogl_object_get_type ();
-}
-
 /* XXX: Unlike for cogl_object_get_user_data this code will return
  * an empty entry if available and no entry for the given key can be
  * found. */