Windows: Match the name case of included files

Although Windows is case insensitive, and lower case always works, Clang
complains:

Lexical or Preprocessor Issue: warning: non-portable path to file
'<FooBar.h>'; specified path differs in case from file name on disk

Change-Id: I8f94e9fb62f6afec8aa6b9d08a7c78f6ba8a4435
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/valgrind/memchecktool.cpp

@@ -102,7 +102,7 @@
 
 #include <utils/winutils.h>
 
-#include <windows.h>
+#include <Windows.h>
 #endif
 
 using namespace Core;