Remove no longer needed undead horse leash patch

This is now default vanilla behavior

Fixes #3644

Spigot-Server-Patches/0158-Implement-ensureServerConversions-API.patch

@@ -0,0 +1,23 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Wed, 4 May 2016 22:43:12 -0400
+Subject: [PATCH] Implement ensureServerConversions API
+
+This will take a Bukkit ItemStack and run it through any conversions a server process would perform on it,
+to ensure it meets latest minecraft expectations.
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/inventory/CraftItemFactory.java b/src/main/java/org/bukkit/craftbukkit/inventory/CraftItemFactory.java
+index 97a58900ac1622e84b8bed87004c7dd85067d31e..efa013a8bf91df0b71cbf01d2c1b1099ac616c57 100644
+--- a/src/main/java/org/bukkit/craftbukkit/inventory/CraftItemFactory.java
++++ b/src/main/java/org/bukkit/craftbukkit/inventory/CraftItemFactory.java
+@@ -326,4 +326,10 @@ public final class CraftItemFactory implements ItemFactory {
+     public Material updateMaterial(ItemMeta meta, Material material) throws IllegalArgumentException {
+         return ((CraftMetaItem) meta).updateMaterial(material);
+     }
++    // Paper start
++    @Override
++    public ItemStack ensureServerConversions(ItemStack item) {
++        return CraftItemStack.asCraftMirror(CraftItemStack.asNMSCopy(item));
++    }
++    // Paper end
+ }