corrected compound example in docs to match current behavior
corrected compound example in docs to match current behavior

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