Doc: remove obsolete \if defined commands

The doc sources are no longer used for single-sourcing.

Change-Id: I934c88c19646d84b4de3c5787234148f947c4489
Reviewed-by: Kai Koehne <kai.koehne@digia.com>

doc/src/qtquick/qtquick-app-development.qdoc

@@ -64,11 +64,9 @@
     \section1 Related Topics
 
     \list
-        \if defined(qcmanual)
         \li \l {Using Qt Quick Designer}
         \li \l {Creating Buttons}
         \li \l {Creating Scalable Buttons and Borders}
-        \endif
         \li \l {Exporting Designs from Graphics Software}
         \li \l {Using QML Modules with Plugins}