sfl_config: remove dead (and illegal) code

This method could never be invoked because we've disallowed
copying.

daemon/src/config/sfl_config.h

@@ -149,10 +149,6 @@ class ConfigTree {
         friend class ConfigTreeIterator;
 
         NON_COPYABLE(ConfigTree);
-    public:
-        ConfigTreeIterator createIterator() {
-            return ConfigTreeIterator(this);
-        }
 };
 
 class ConfigTreeItem {