💚 Make the "invalid" Babel fixture throw

Due to the V8 upgrade we need to tune the fixture to make it throw.
Using a generator function does the trick ⚡

spec/fixtures/babel/invalid.js

@@ -1,3 +1,3 @@
 'use 6to6';
 
-module.exports = async function hello() {}
+module.exports = async function* hello() {}