fix test_regression_6236
fix test_regression_6236

The regression tes in question actually re-worked the representation parameter... which we forgot to rename along side everything in the actual code.

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