Welcome: fix link to mobile app tutorial

The tutorial filename was changed.

Task-number: QTCREATORBUG-12247

Change-Id: Ibb2733e41807757c2ce435a0b918eada4da99665
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

share/qtcreator/welcomescreen/qtcreator_tutorials.xml

@@ -17,7 +17,7 @@
       <description><![CDATA[Using basic QML elements and learning about basic concepts of Qt Quick.]]></description>
       <tags>qt creator,qt quick designer,qt quick,qml,states,transitions</tags>
     </tutorial>
-    <tutorial imageUrl="images/icons/androidapp.png" difficulty="" docUrl="qthelp://org.qt-project.qtcreator/doc/creator-android-app-tutorial.html" projectPath="" name="Creating a Mobile Application">
+    <tutorial imageUrl="images/icons/androidapp.png" difficulty="" docUrl="qthelp://org.qt-project.qtcreator/doc/creator-mobile-app-tutorial.html" projectPath="" name="Creating a Mobile Application">
       <description><![CDATA[Developing Qt Quick applications for Android and iOS devices using Qt Quick Controls.]]></description>
       <tags>qt creator,qt quick designer,qml,android</tags>
     </tutorial>