minor tweak to wording in docs [ci skip]
minor tweak to wording in docs [ci skip]

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