xfce-icon-theme: fix QA warnings

* xfce4-icon-theme-4.4.3: xfce4-icon-theme: Files/directories were installed but not shipped
  /usr/share/xfce4
  /usr/share/xfce4/mime
  /usr/share/xfce4/mime/Rodent.mime.xml

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>