doc: fixed error in uix/widget.py
doc: fixed error in uix/widget.py

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