Tests: fix missing include

Change-Id: Ibcfe19529aae58c1efcb806f2cd728224ba3b2f7
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

tests/auto/solutions/qprocesstask/testsleep/main.cpp

@@ -1,6 +1,7 @@
 // Copyright (C) 2023 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
 
+#include <chrono>
 #include <thread>
 
 using namespace std;