Remove broken link to es6 interactive tutotial (#7203)

more/free-programming-interactive-tutorials-en.md

@@ -204,7 +204,6 @@
 
 * [ABC of JavaScript : An Interactive JavaScript Tutorial](http://www.openjs.com/tutorials/basic_tutorial/)
 * [Codecademy jquery track](https://www.codecademy.com/learn/jquery)
-* [ES6 Interactive Guide](http://stack.formidable.com/es6-interactive-guide/#/)
 * [Functional Programming in Javascript](https://github.com/ReactiveX/learnrx)
 * [JavaScript Algorithms and Data Structures Certification](https://www.freecodecamp.org/learn/javascript-algorithms-and-data-structures/) - freeCodeCamp
 * [JavaScript interactive tutorial on CodeCademy](https://www.codecademy.com/learn/javascript)