add missing backtick
add missing backtick

[docs only]

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