Use QThread instead of QPushButton as an example in the docs

This keeps links local and inside the module.

Change-Id: I5e267197c6356a2c4e231c1941ed4be33b96a16e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/doc/snippets/code/src_corelib_kernel_qmetaobject.cpp

@@ -62,7 +62,7 @@ QByteArray normType = QMetaObject::normalizedType(" int    const  *");
 
 
 //! [2]
-QMetaObject::invokeMethod(pushButton, "animateClick",
+QMetaObject::invokeMethod(thread, "quit",
                           Qt::QueuedConnection);
 //! [2]
 

src/corelib/kernel/qmetaobject.cpp

@@ -1375,8 +1375,8 @@ enum { MaximumParamCount = 11 }; // up to 10 arguments + 1 return value
 
     You only need to pass the name of the signal or slot to this function,
     not the entire signature. For example, to asynchronously invoke
-    the \l{QPushButton::animateClick()}{animateClick()} slot on a
-    QPushButton, use the following code:
+    the \l{QThread::quit()}{quit()} slot on a
+    QThread, use the following code:
 
     \snippet code/src_corelib_kernel_qmetaobject.cpp 2