Update to Minecraft 1.15

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

paper-server/nms-patches/DamageSource.patch

@@ -17,5 +17,5 @@
 +    }
 +    // CraftBukkit end
  
-     public static DamageSource mobAttack(EntityLiving entityliving) {
-         return new EntityDamageSource("mob", entityliving);
+     public static DamageSource a(EntityLiving entityliving) {
+         return new EntityDamageSource("sting", entityliving);