[DOC] recipes.rst uses Twig_Function_Function
[DOC] recipes.rst uses Twig_Function_Function

Hello,
Here's a minor update for recipes.rst
I rewrite the code sample for registerUndefinedFunctionCallback to remove usage of deprecated class Twig_Function_Function.
nicolas-grekas/Twig,gencer/Twig,gamernetwork/Twig,gamernetwork/Twig,nicolas-grekas/Twig,gamernetwork/Twig,nicolas-grekas/Twig,twigphp/Twig,nicolas-grekas/Twig,gencer/Twig,nicolas-grekas/Twig,twigphp/Twig,twigphp/Twig