Doc: Fix broken return codes for a few examples

This reverts remnants of 79747d38987ce42adc510be0c5bb1565f55fd3d6.

Task-number: QTBUG-25571
Change-Id: I1dbf64cfcba889fb0c70ceaeeeffad8334a8aab1
Reviewed-by: Casper van Donderen <casper.vandonderen@nokia.com>

examples/network/fortuneclient/main.cpp

@@ -46,5 +46,5 @@ int main(int argc, char *argv[])
     QApplication app(argc, argv);
     Client client;
     client.show();
-    return client.exec();
+    return app.exec();
 }

examples/network/fortuneserver/main.cpp

@@ -51,5 +51,5 @@ int main(int argc, char *argv[])
     Server server;
     server.show();
     qsrand(QTime(0,0,0).secsTo(QTime::currentTime()));
-    return server.exec();
+    return app.exec();
 }

examples/network/multicastreceiver/main.cpp

@@ -47,5 +47,5 @@ int main(int argc, char *argv[])
     QApplication app(argc, argv);
     Receiver receiver;
     receiver.show();
-    return receiver.exec();
+    return app.exec();
 }

examples/network/multicastsender/main.cpp

@@ -47,5 +47,5 @@ int main(int argc, char *argv[])
     QApplication app(argc, argv);
     Sender sender;
     sender.show();
-    return sender.exec();
+    return app.exec();
 }

examples/tools/regexp/main.cpp

@@ -47,5 +47,5 @@ int main(int argc, char *argv[])
     QApplication app(argc, argv);
     RegExpDialog dialog;
     dialog.show();
-    return dialog.exec();
+    return app.exec();
 }