Remove a ClangImporter function that I noticed is no longer in use.

Author: rudkx

lib/ClangImporter/ImportType.cpp

@@ -2709,10 +2709,3 @@ Type ClangImporter::Implementation::getNSCopyingType() {
 Type ClangImporter::Implementation::getNSObjectProtocolType() {
   return getNamedProtocolType(*this, "NSObject");
 }
-
-Type ClangImporter::Implementation::getCFStringRefType() {
-  if (auto decl = dyn_cast_or_null<TypeDecl>(importDeclByName("CFStringRef")))
-    return decl->getDeclaredType();
-  return Type();
-}
-

lib/ClangImporter/ImporterImpl.h

@@ -1158,9 +1158,6 @@ class LLVM_LIBRARY_VISIBILITY ClangImporter::Implementation
   /// \brief Retrieve the NSCopying protocol type.
   Type getNSCopyingType();
 
-  /// \brief Retrieve the CFStringRef typealias.
-  Type getCFStringRefType();
-
   /// \brief Determines whether the given type matches an implicit type
   /// bound of "Hashable", which is used to validate NSDictionary/NSSet.
   bool matchesNSObjectBound(Type type);