Fix typo in ProgressBar
Fix typo in ProgressBar

Closes #4649
akshayaurora/kivy,matham/kivy,jegger/kivy,kived/kivy,jegger/kivy,jkankiewicz/kivy,bionoid/kivy,kivy/kivy,bionoid/kivy,kived/kivy,KeyWeeUsr/kivy,manthansharma/kivy,janssen/kivy,janssen/kivy,kivy/kivy,rafalo1333/kivy,inclement/kivy,tony/kivy,autosportlabs/kivy,LogicalDash/kivy,rafalo1333/kivy,LogicalDash/kivy,Cheaterman/kivy,janssen/kivy,LogicalDash/kivy,darkopevec/kivy,bionoid/kivy,manthansharma/kivy,darkopevec/kivy,inclement/kivy,jkankiewicz/kivy,KeyWeeUsr/kivy,rnixx/kivy,jegger/kivy,tony/kivy,matham/kivy,matham/kivy,matham/kivy,manthansharma/kivy,jkankiewicz/kivy,akshayaurora/kivy,akshayaurora/kivy,jegger/kivy,Cheaterman/kivy,LogicalDash/kivy,inclement/kivy,KeyWeeUsr/kivy,jkankiewicz/kivy,rafalo1333/kivy,tony/kivy,autosportlabs/kivy,rnixx/kivy,manthansharma/kivy,kived/kivy,KeyWeeUsr/kivy,bionoid/kivy,Cheaterman/kivy,kivy/kivy,darkopevec/kivy,rnixx/kivy,janssen/kivy,darkopevec/kivy,autosportlabs/kivy,Cheaterman/kivy