Only require polling when running on Windows XP

Since the restriction for what gets notified for Wireless network
configurations is only on Windows XP then we only want to do polling on
Windows XP. This gives a performance boost as it does not query every 10
seconds for no reason.

Task-number: QTBUG-40332
Change-Id: I73e3903834abe9ffc5adc678de20f7428a578d89
Reviewed-by: Richard J. Moore <rich@kde.org>

src/plugins/bearer/nativewifi/qnativewifiengine.cpp

@@ -606,7 +606,7 @@ bool QNativeWifiEngine::requiresPolling() const
 {
     // On Windows XP SP2 and SP3 only connection and disconnection notifications are available.
     // We need to poll for changes in available wireless networks.
-    return true;
+    return QSysInfo::WindowsVersion <= QSysInfo::WV_2003;
 }
 
 QT_END_NAMESPACE