QTimer: add note about QT_NO_CONTEXTLESS_CONNECT to callOnTimeout docs

Drive-by change: use \code, better formatting especially for longer
lines of code.

Change-Id: I90dbde17a5bea276c86304bff64027dd9d248a21
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/kernel/qtimer.cpp

@@ -516,6 +516,9 @@ void QTimer::singleShot(int msec, Qt::TimerType timerType, const QObject *receiv
     QObject::connect(timer, &QTimer::timeout, timer, slot, Qt::DirectConnection);
     \endcode
 
+    \note This overload is not available when \c {QT_NO_CONTEXTLESS_CONNECT} is
+    defined, instead use the callOnTimeout() overload that takes a context object.
+
     \sa QObject::connect(), timeout()
 */
 
@@ -527,8 +530,10 @@ void QTimer::singleShot(int msec, Qt::TimerType timerType, const QObject *receiv
     Creates a connection from the timeout() signal to \a slot to be placed in a specific
     event loop of \a context, and returns a handle to the connection.
 
-    This method is provided for convenience. It's equivalent to calling
-    \c {QObject::connect(timer, &QTimer::timeout, context, slot, connectionType)}.
+    This method is provided for convenience. It's equivalent to calling:
+    \code
+    QObject::connect(timer, &QTimer::timeout, context, slot, connectionType);
+    \endcode
 
     \sa QObject::connect(), timeout()
 */