chore: XWindowScreenSave, use auto where possible

src/lib/platform/XWindowsScreenSaver.cpp

@@ -426,7 +426,7 @@ void XWindowsScreenSaver::clearWatchForXScreenSaver()
 {
   // stop watching all windows
   XWindowsUtil::ErrorLock lock(m_display);
-  for (WatchList::iterator index = m_watchWindows.begin(); index != m_watchWindows.end(); ++index) {
+  for (auto index = m_watchWindows.begin(); index != m_watchWindows.end(); ++index) {
     XSelectInput(m_display, index->first, index->second);
   }
   m_watchWindows.clear();