Remove duplicated case.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@184640 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/FrontendOptions.cpp b/lib/Frontend/FrontendOptions.cpp
index f1823c6..1869d0c 100644
--- a/lib/Frontend/FrontendOptions.cpp
+++ b/lib/Frontend/FrontendOptions.cpp
@@ -22,7 +22,6 @@
     .Case("mi", IK_PreprocessedObjC)
     .Cases("mm", "M", IK_ObjCXX)
     .Case("mii", IK_PreprocessedObjCXX)
-    .Case("C", IK_CXX)
     .Cases("C", "cc", "cp", IK_CXX)
     .Cases("cpp", "CPP", "c++", "cxx", "hpp", IK_CXX)
     .Case("cl", IK_OpenCL)