doc: update download instructions for Kivy.app
doc: update download instructions for Kivy.app

jkankiewicz/kivy,janssen/kivy,tony/kivy,LogicalDash/kivy,rafalo1333/kivy,LogicalDash/kivy,Cheaterman/kivy,jegger/kivy,manthansharma/kivy,bionoid/kivy,KeyWeeUsr/kivy,akshayaurora/kivy,matham/kivy,jkankiewicz/kivy,jegger/kivy,rafalo1333/kivy,kived/kivy,Cheaterman/kivy,bionoid/kivy,jkankiewicz/kivy,manthansharma/kivy,tony/kivy,LogicalDash/kivy,jkankiewicz/kivy,KeyWeeUsr/kivy,KeyWeeUsr/kivy,rafalo1333/kivy,kived/kivy,kivy/kivy,matham/kivy,manthansharma/kivy,bionoid/kivy,akshayaurora/kivy,autosportlabs/kivy,matham/kivy,janssen/kivy,akshayaurora/kivy,kivy/kivy,bionoid/kivy,rnixx/kivy,inclement/kivy,inclement/kivy,LogicalDash/kivy,rnixx/kivy,janssen/kivy,janssen/kivy,kivy/kivy,matham/kivy,tony/kivy,autosportlabs/kivy,jegger/kivy,manthansharma/kivy,kived/kivy,inclement/kivy,jegger/kivy,rnixx/kivy,Cheaterman/kivy,KeyWeeUsr/kivy,autosportlabs/kivy,Cheaterman/kivy