Doc: feedback button has been removed from Welcome mode

Remove text accordingly.

Change-Id: Ief3a36ecd7f83dee7c40c4b45da15c5ad185e550
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>

doc/src/howto/creator-ui.qdoc

@@ -42,8 +42,6 @@
 
         \li Read news from the online community and Qt labs
 
-        \li Send feedback to the development team
-
     \endlist
 
     \image qtcreator-breakdown.png