Fix sphinx error and typo.
Fix sphinx error and typo.

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