SPIGOT-5591: Allow concurrent potion effects

By: md_5 <git@md-5.net>

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java

@@ -321,12 +321,6 @@ public class CraftLivingEntity extends CraftEntity implements LivingEntity {
 
     @Override
     public boolean addPotionEffect(PotionEffect effect, boolean force) {
-        if (hasPotionEffect(effect.getType())) {
-            if (!force) {
-                return false;
-            }
-            removePotionEffect(effect.getType());
-        }
         getHandle().addEffect(new MobEffect(MobEffectList.fromId(effect.getType().getId()), effect.getDuration(), effect.getAmplifier(), effect.isAmbient(), effect.hasParticles()), EntityPotionEffectEvent.Cause.PLUGIN);
         return true;
     }