fix some typos.
fix some typos.

[ci skip]

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