[Xcode] Remove duplicated CFDateFormatter entries
[Xcode] Remove duplicated CFDateFormatter entries

This addresses the warning of ":-1: Skipping duplicate build file in Copy Headers build phase: /Users/ikesyo/swift-source/swift-corelibs-foundation/CoreFoundation/Locale.subproj/CFDateFormatter.h (in target 'CoreFoundation')".

e78l/swift-corelibs-foundation,parkera/swift-corelibs-foundation,e78l/swift-corelibs-foundation,parkera/swift-corelibs-foundation,e78l/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,e78l/swift-corelibs-foundation,parkera/swift-corelibs-foundation,parkera/swift-corelibs-foundation,parkera/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,e78l/swift-corelibs-foundation