Update watchOS deployment target for submission to Apple
Update watchOS deployment target for submission to Apple

It appears that, while unpublished, Apple is requiring all watchOS deployment targets to be updated to 3.0

https://forums.developer.apple.com/thread/108853 for reference

Addresses https://github.com/ReactiveX/RxSwift/issues/1752

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