Win: Get rid of unused variables un QDateTime::currentMSecsSinceEpoch

The compiler didn't complain that they were unused or -Werror / -WX was
not active.

Change-Id: Ib57b52598e2f452985e9fffd145a7b63a32189fd
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@qt.io>

src/corelib/tools/qdatetime.cpp

@@ -4118,8 +4118,6 @@ QDateTime QDateTime::currentDateTimeUtc()
 
 qint64 QDateTime::currentMSecsSinceEpoch() Q_DECL_NOTHROW
 {
-    QDate d;
-    QTime t;
     SYSTEMTIME st;
     memset(&st, 0, sizeof(SYSTEMTIME));
     GetSystemTime(&st);