Add test case

Author: localspook

clang-tools-extra/test/clang-tidy/checkers/readability/redundant-typename.cpp

@@ -203,6 +203,7 @@ class A {
   // CHECK-FIXES-20: friend void k(T::R) {}
 
   friend struct T::R;
+  using typename T::R;
   enum E1 : typename T::R {};
   enum class E2 : typename T::R {};
   operator typename T::R();