Update to Minecraft 1.13.1

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

paper-server/src/test/java/org/bukkit/entity/EntityTypesTest.java

@@ -4,6 +4,7 @@ import java.util.Arrays;
 import java.util.Set;
 import java.util.stream.Collectors;
 import net.minecraft.server.EntityTypes;
+import net.minecraft.server.IRegistry;
 import net.minecraft.server.MinecraftKey;
 import org.junit.Assert;
 import org.junit.Test;
@@ -14,7 +15,7 @@ public class EntityTypesTest {
     public void testMaps() {
         Set<EntityType> allBukkit = Arrays.stream(EntityType.values()).filter((b) -> b.getName() != null).collect(Collectors.toSet());
 
-        for (Object o : EntityTypes.REGISTRY) {
+        for (Object o : IRegistry.ENTITY_TYPE) {
             EntityTypes<?> nms = (EntityTypes<?>) o; // Eclipse fail
             MinecraftKey key = EntityTypes.getName(nms);