Fix a couple of minor doc issues [skip ci]
Fix a couple of minor doc issues [skip ci]

larrybradley/astropy,saimn/astropy,larrybradley/astropy,saimn/astropy,larrybradley/astropy,astropy/astropy,StuartLittlefair/astropy,lpsinger/astropy,pllim/astropy,astropy/astropy,StuartLittlefair/astropy,mhvk/astropy,saimn/astropy,larrybradley/astropy,StuartLittlefair/astropy,mhvk/astropy,saimn/astropy,lpsinger/astropy,astropy/astropy,mhvk/astropy,mhvk/astropy,lpsinger/astropy,pllim/astropy,mhvk/astropy,saimn/astropy,lpsinger/astropy,pllim/astropy,lpsinger/astropy,StuartLittlefair/astropy,pllim/astropy,astropy/astropy,StuartLittlefair/astropy,astropy/astropy,larrybradley/astropy,pllim/astropy