A flash of light streaks toward a creature of your choice within range. Make a ranged spell attack against the target. On a hit, the target takes 4d6 radiant damage, and the next attack roll made against this target before the end of your next turn has advantage, thanks to the mystical dim light glittering on the target until then.

Maybe I'm misunderstanding something and the phrasing isn't perfect but I'd say the combination of saying that the advantage is caused by the light and the advantage lasting to the end of your next turn would mean that the light also lasts until the end of your next turn?