XCode -> Xcode (#4699)

Carthage.md

@@ -88,7 +88,7 @@ binary "https://dl.google.com/dl/firebase/ios/carthage/FirebaseStorageBinary.jso
      [upload-symbols](https://github.com/firebase/firebase-ios-sdk/raw/master/Crashlytics/upload-symbols)
      and [run](https://github.com/firebase/firebase-ios-sdk/raw/master/Crashlytics/run).
      Then follow the [Crashlytics documentation](https://firebase.google.com/docs/crashlytics/get-started-new-sdk?platform=ios)
-     to add a new run script phase in your XCode project.
+     to add a new run script phase in your Xcode project.
 
 ## Versioning