Fixed warning with CocoaPods

CocoaPods had been barfing out this(https://cloudup.com/cZ00hmv4nje) error whenever you'd run `pod install`. The source of the problem was from this PR(https://github.com/wordpress-mobile/WordPress-iOS/pull/2609) and in particular this change set(https://github.com/wordpress-mobile/WordPress-iOS/pull/2609/files#diff-af2e9c080d966c7e1d58ca2dc0dcc251R1277). The merge snuck files into the Xcode project that had been previously deleted. Apparently when CocoaPods would try to generate the project it would spit out that warning because of it.