Update docs on known issues; see astropy/astropy/#7582 [docs only]
Update docs on known issues; see astropy/astropy/#7582 [docs only]

StuartLittlefair/astropy,pllim/astropy,aleksandr-bakanov/astropy,stargaser/astropy,saimn/astropy,StuartLittlefair/astropy,mhvk/astropy,astropy/astropy,bsipocz/astropy,lpsinger/astropy,dhomeier/astropy,stargaser/astropy,aleksandr-bakanov/astropy,MSeifert04/astropy,MSeifert04/astropy,saimn/astropy,MSeifert04/astropy,StuartLittlefair/astropy,larrybradley/astropy,larrybradley/astropy,mhvk/astropy,mhvk/astropy,astropy/astropy,dhomeier/astropy,MSeifert04/astropy,lpsinger/astropy,stargaser/astropy,dhomeier/astropy,pllim/astropy,lpsinger/astropy,StuartLittlefair/astropy,bsipocz/astropy,lpsinger/astropy,bsipocz/astropy,lpsinger/astropy,larrybradley/astropy,pllim/astropy,dhomeier/astropy,stargaser/astropy,astropy/astropy,larrybradley/astropy,mhvk/astropy,astropy/astropy,pllim/astropy,aleksandr-bakanov/astropy,saimn/astropy,larrybradley/astropy,bsipocz/astropy,astropy/astropy,saimn/astropy,pllim/astropy,mhvk/astropy,dhomeier/astropy,saimn/astropy,StuartLittlefair/astropy,aleksandr-bakanov/astropy