Update CONTRIBUTING.md
Update CONTRIBUTING.md

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