Remove the redundant `SWIFT_VERSION` added by the migrator.
Remove the redundant `SWIFT_VERSION` added by the migrator.

sandyway/ReactiveCocoa,sandyway/ReactiveCocoa,sandyway/ReactiveCocoa,ReactiveCocoa/ReactiveSwift,ReactiveCocoa/ReactiveSwift,walkingsmarts/ReactiveCocoa,ohwutup/ReactiveCocoa,ohwutup/ReactiveCocoa,calebd/ReactiveCocoa,ikesyo/ReactiveCocoa,walkingsmarts/ReactiveCocoa,victorlin/ReactiveCocoa,walkingsmarts/ReactiveCocoa,ohwutup/ReactiveCocoa,ikesyo/ReactiveCocoa,victorlin/ReactiveCocoa,ReactiveCocoa/ReactiveSwift,calebd/ReactiveCocoa,calebd/ReactiveCocoa,victorlin/ReactiveCocoa