`UITextWritingDirection` deprecation warning

[iamgabrielma]

Since iOS13.0 the usage of the UITextWritingDirection typealias is deprecated in favour of the existing underlying NSWritingDirection data type: https://developer.apple.com/documentation/uikit/uitextwritingdirection

Since we use these as the return type when defining methods like baseWritingDirectionForPosition in the header file, it causes warnings in the editor where this dependency is used. For example in WCiOS:

'UITextWritingDirection' is deprecated: first deprecated in iOS 13.0