doc: Correct remaining qdoc warning in qstate.cpp

clang required adding template clause to a \fn command.

Change-Id: Icbe0557f7fa67ba211df5cfbc68baa6cf737d7b1
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>

src/corelib/statemachine/qstate.cpp

@@ -341,8 +341,7 @@ void QState::addTransition(QAbstractTransition *transition)
 }
 
 /*!
-  \fn QState::addTransition(const QObject *sender, PointerToMemberFunction signal,
-                       QAbstractState *target);
+  \fn template <typename PointerToMemberFunction> QState::addTransition(const QObject *sender, PointerToMemberFunction signal, QAbstractState *target);
   \since 5.5
   \overload