Change AstropyUserWarning -> AstropyWarning in warnings docs
Change AstropyUserWarning -> AstropyWarning in warnings docs

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