Protocol modifying the Agreement of 9 February 1994 on the levying of a user charge for the use of certain roads by heavy goods vehicles according to Directive 2011/76/EU of the European Parliament and of the Council of 27 September 2011 modifying Directive 1999/62/EC of the European Parliament and of the Council of 17 June 1999 on the charging of heavy goods vehicles for the use of certain infrastructures