fix doc typo
fix doc typo

mhvk/astropy,saimn/astropy,mhvk/astropy,DougBurke/astropy,bsipocz/astropy,kelle/astropy,kelle/astropy,lpsinger/astropy,AustereCuriosity/astropy,larrybradley/astropy,pllim/astropy,stargaser/astropy,bsipocz/astropy,lpsinger/astropy,larrybradley/astropy,funbaker/astropy,StuartLittlefair/astropy,funbaker/astropy,saimn/astropy,stargaser/astropy,DougBurke/astropy,lpsinger/astropy,MSeifert04/astropy,dhomeier/astropy,pllim/astropy,kelle/astropy,MSeifert04/astropy,aleksandr-bakanov/astropy,StuartLittlefair/astropy,dhomeier/astropy,astropy/astropy,pllim/astropy,dhomeier/astropy,StuartLittlefair/astropy,bsipocz/astropy,StuartLittlefair/astropy,DougBurke/astropy,aleksandr-bakanov/astropy,AustereCuriosity/astropy,mhvk/astropy,dhomeier/astropy,AustereCuriosity/astropy,astropy/astropy,kelle/astropy,astropy/astropy,pllim/astropy,stargaser/astropy,mhvk/astropy,saimn/astropy,mhvk/astropy,funbaker/astropy,AustereCuriosity/astropy,astropy/astropy,saimn/astropy,MSeifert04/astropy,aleksandr-bakanov/astropy,StuartLittlefair/astropy,saimn/astropy,lpsinger/astropy,dhomeier/astropy,aleksandr-bakanov/astropy,larrybradley/astropy,AustereCuriosity/astropy,stargaser/astropy,kelle/astropy,larrybradley/astropy,funbaker/astropy,bsipocz/astropy,MSeifert04/astropy,larrybradley/astropy,astropy/astropy,DougBurke/astropy,pllim/astropy,lpsinger/astropy