Update ch07-02-defining-modules-to-control-scope-and-privacy.md

[0xSaksham]

I found some grammar errors while reading the book and a ( , ) comma missing making it hard to interpret what message the author was trying to convey.

[chriskrycho]

Thanks for the PR! As it turns out, the original text here is either more correct or at least as correct as the suggested changes, although you might have to read some of the passages carefully to see why that is so. I am going to go ahead close this accordingly. We appreciate your caring about this level of detail, though!