Revert "API: Add API to set style properties to be inherit"

Inheritance is now done using style property flags, so thereis no ned
anymore to clobber the pspec flags namespace.
Also, there is no need to expose this functionality in the public API
without exposing more of the styleproperty API.

This essentially reverts commit 9bfd3d2eec.

gtk/gtkstyleproperty.c

@@ -1946,8 +1946,7 @@ _gtk_style_property_is_inherit (const GtkStyleProperty *property)
 {
   g_return_val_if_fail (property != NULL, FALSE);
 
-  return property->flags & GTK_STYLE_PROPERTY_INHERIT ||
-    gtk_style_param_get_inherit (property->pspec);
+  return property->flags & GTK_STYLE_PROPERTY_INHERIT ? TRUE : FALSE;
 }
 
 gboolean