Pillagers do not shoot fireworks from their offhand

The bug

When you summon a pillager with fireworks in its offhand, it does not shoot them as the player does.

Steps to reproduce

1. Summon a pillager holding a crossbow and a firework rocket

   /summon minecraft:pillager ~ ~ ~ {HandItems:[{id:"crossbow",Count:1b},{id:"firework_rocket",Count:1b}]}

2. Let it shoot you
   → Notice it shoots arrows instead of fireworks