Fix valid data output quickstart.md

[Arhell]

What are you trying to achieve?

fix valid data output

What do you get instead?

https://validator.w3.org/nu/?doc=https%3A%2F%2Fcodecept.io%2Fquickstart%2F

Details

update docs
https://github.com/codecept-js/CodeceptJS/blob/master/docs/quickstart.md

I will correct

[Arhell]

done