remove comment on header that is likely to become stale

Author: bob80905

tools/clang/unittests/HLSL/ValidationTest.cpp

@@ -25,7 +25,7 @@
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Regex.h"
-#include <wchar.h> // for _wgetenv
+#include <wchar.h>
 
 #ifdef _WIN32
 #include <atlbase.h>