Fake forecast is already uncommented

[arthurevans]

Step 4 says, "uncomment the line below at the bottom of your scripts/app.js file."

However, it already is:

https://github.com/googlecodelabs/your-first-pwapp/blob/master/step-04/scripts/app.js#L178

... which is a little confusing.

[petele]

Fixed in the master doc, should get rolled out shortly.

/cc @marcacohen

[mco-gh]

The step dirs reflect the end state of a given step so it's correct that the step-04 copy should have the line uncommented.