[KCFI][NFC] Remove unused header (#170599)

In addition to being unused, this forms a layering violation between
Transforms/Utils and Transforms/Instrumentation

Author: rupprecht

llvm/lib/Transforms/Utils/ModuleUtils.cpp

@@ -22,7 +22,6 @@
 #include "llvm/Support/Hash.h"
 #include "llvm/Support/MD5.h"
 #include "llvm/Support/raw_ostream.h"
-#include "llvm/Transforms/Instrumentation/KCFI.h"
 
 using namespace llvm;