Update BJD conversion info in docstring
Update BJD conversion info in docstring

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