Bright Reprisal
Oracle Text
Destroy target attacking creature.
Draw a card.
Card Rulings
9/29/2017 If the target creature is an illegal target by the time Bright Reprisal resolves, the entire spell doesn’t resolve. You won’t draw a card. If, on the other hand, the target is a legal target but isn’t destroyed (most likely because it has indestructible), you’ll draw a card.
The knight is clearly charging the dinosaur which makes the knight the attacking creature. Yes, a lance can be used to set against a charge and would qualify as a reprisal against an attack, but that's clearly not what's happening here. You don't set for a charge while galloping at the enemy and holding your lance in one hand.