cleaner use of differentials in docs
cleaner use of differentials in docs

Co-Authored-By: Adrian Price-Whelan <3738087e476317196ac2db7cf211c8325d8d8040@gmail.com>
saimn/astropy,astropy/astropy,pllim/astropy,mhvk/astropy,dhomeier/astropy,StuartLittlefair/astropy,saimn/astropy,aleksandr-bakanov/astropy,lpsinger/astropy,aleksandr-bakanov/astropy,saimn/astropy,lpsinger/astropy,lpsinger/astropy,larrybradley/astropy,aleksandr-bakanov/astropy,larrybradley/astropy,dhomeier/astropy,dhomeier/astropy,dhomeier/astropy,saimn/astropy,pllim/astropy,astropy/astropy,mhvk/astropy,astropy/astropy,astropy/astropy,astropy/astropy,mhvk/astropy,larrybradley/astropy,lpsinger/astropy,mhvk/astropy,lpsinger/astropy,saimn/astropy,pllim/astropy,pllim/astropy,StuartLittlefair/astropy,dhomeier/astropy,StuartLittlefair/astropy,pllim/astropy,larrybradley/astropy,StuartLittlefair/astropy,mhvk/astropy,StuartLittlefair/astropy,aleksandr-bakanov/astropy,larrybradley/astropy