Unlike a spell like fire bolt which targets an enemy, The range of true strike is “Self” so, no it doesn’t give you advantage to attack someone else.
All the spell does is enhance your ability to attack by letting you attack with your spellcasting ability and change the damage to radiant if you hit. Basically, it’s a buffing spell, not an attack spell.
It’s the equivalent of using Enhance ability to boost your strength and then saying you get advantage on all melee attacks while the spell is up because you cast it as a sorcerer spell.