[SHLWAPI_APITEST] Fix MSVC compilation warning C4309

SHPropertyBag.cpp(161): warning C4309: 'initializing': truncation of constant value

See https://stackoverflow.com/questions/33333448/warning-c4309-what-does-it-mean-and-can-it-be-ignored-in-this-case
for some details.

modules/rostests/apitests/shlwapi/SHPropertyBag.cpp

@@ -158,7 +158,7 @@ static void SHPropertyBag_ReadTest(void)
     HRESULT hr;
     CDummyPropertyBag dummy;
     BOOL bValue = 0xDEADFACE;
-    SHORT sValue = 0xDEAD;
+    SHORT sValue = 0xDEADu;
     LONG lValue = 0xDEADDEAD;
     DWORD dwValue = 0xFEEDF00D;
     BSTR bstr = NULL;