Remove single-argument cReduce tests in js2/9

[bryanjenningz]

• The reason why we're removing the single-argument cReduce tests is because the cReduce descriptions says: "It is best practice to pass in 2 arguments into reduce function. Therefore, for this challenge, you can assume that when your function, cReduce, will always be called with 2 arguments: a function and initial value."
• See the description for cReduce at: https://www.c0d3.com/curriculum/js2?challenge=129