[API notes] CTFontManagerError is not a valid Error at this time. (#4104)

CoreText is below Foundation in the framework stack, so its error enum
uses a CFStringRef constant as its domain instead of an NSString. The
importer doesn't know how to handle that yet, so for now, just don't
import CTFontManagerError as a first-class error type.

rdar://problem/27722004

Author: jrose-apple

apinotes/CoreText.apinotes

@@ -1,8 +1,5 @@
 ---
 Name: CoreText
-Tags:
-- Name: CTFontManagerError
-  NSErrorDomain: kCTFontManagerErrorDomain
 Enumerators:
 - Name: kCTUnderlinePatternSolid
   SwiftName: patternSolid