Remove "Auto fix bad Y levels on player login" patch

Fixes #6357
Closes #6508
Closes #6358

patches/server/0123-Properly-fix-item-duplication-bug.patch

@@ -0,0 +1,33 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Alfie Cleveland <alfeh@me.com>
+Date: Tue, 27 Dec 2016 01:57:57 +0000
+Subject: [PATCH] Properly fix item duplication bug
+
+Credit to prplz for figuring out the real issue
+
+diff --git a/src/main/java/net/minecraft/server/level/ServerPlayer.java b/src/main/java/net/minecraft/server/level/ServerPlayer.java
+index 7e7bbb6817ceddbbb90c1ac45d8e974d3f95c089..d4614faa22485dce226f3dc17ef984212ac8fcb9 100644
+--- a/src/main/java/net/minecraft/server/level/ServerPlayer.java
++++ b/src/main/java/net/minecraft/server/level/ServerPlayer.java
+@@ -2128,7 +2128,7 @@ public class ServerPlayer extends Player {
+ 
+     @Override
+     public boolean isImmobile() {
+-        return super.isImmobile() || !this.getBukkitEntity().isOnline();
++        return super.isImmobile() || (this.connection != null && this.connection.isDisconnected()); // Paper
+     }
+ 
+     @Override
+diff --git a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+index 9026dd91f8d874209bbfd4cdfd3c41e37cdd7560..6eb01dcf59fda2656b6d93b0c39380302665f930 100644
+--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
++++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+@@ -2810,7 +2810,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Ser
+     }
+ 
+     public final boolean isDisconnected() {
+-        return !this.player.joining && !this.connection.isConnected();
++        return (!this.player.joining && !this.connection.isConnected()) || this.processedDisconnect; // Paper
+     }
+     // CraftBukkit end
+