QtQuick: Fix & clean up alarms.pro

The current example didn't compile on Windows, because all Qt examples
require a target file.

Also clean up unnecessary parts generated by the Qt Creator wizard.

Change-Id: I40b834e544a146d3e232844e667d568b102bec5c
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>