Make AreaEffectCloudApplyEvent cancellable

nms-patches/EntityAreaEffectCloud.patch

@@ -52,7 +52,7 @@
 +                            }
 +                        }
 +                        org.bukkit.event.entity.AreaEffectCloudApplyEvent event = org.bukkit.craftbukkit.event.CraftEventFactory.callAreaEffectCloudApplyEvent(this, entities);
-+                        if (true) { // Preserve NMS spacing and bracket count for smallest diff
++                        if (!event.isCancelled()) {
 +                            for (LivingEntity entity : event.getAffectedEntities()) {
 +                                if (entity instanceof CraftLivingEntity) {
 +                                    EntityLiving entityliving = ((CraftLivingEntity) entity).getHandle();