Update RxPlaygrounds.swift Comment
Update RxPlaygrounds.swift Comment

I changed line 3 of RxPlaygrounds.swift from `// RxPlaygrounds` to
`// RxExample` because of some build validation check.

kzaher/RxSwift,kzaher/RxSwift,kzaher/RxSwift,ReactiveX/RxSwift,kzaher/RxSwift,ReactiveX/RxSwift,ReactiveX/RxSwift