Remove "Implement-Chunk-Priority-Urgency-System-for-Chunks" (Fixes #5980)

Mojang made some changes to priorities in 1.17 and it seems that these changes
conflict with the changes made in this patch, which in some cases appears to
cause excessive rescheduling of tasks.

This, however, is not confirmed as such but seems to be the behavior that we're
seeing to cause this issue, if mojang has adopted the changes we suggested,
then a good chunk of this patch may be unneeded, but, this needs a much better
look than I'm currently able to do

patches/server/0597-Remove-stale-POIs.patch

@@ -0,0 +1,22 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Shane Freeder <theboyetronic@gmail.com>
+Date: Sat, 9 Jan 2021 14:17:07 +0100
+Subject: [PATCH] Remove stale POIs
+
+
+diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
+index 01abe5e21639b990e5ae6d2021cd86149ddf93e5..4223d4610b4fec588980dba2ea5ec4f04c45d945 100644
+--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
++++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
+@@ -1703,6 +1703,11 @@ public class ServerLevel extends Level implements WorldGenLevel {
+             });
+             optional1.ifPresent((villageplacetype) -> {
+                 this.getServer().execute(() -> {
++                    // Paper start
++                    if (!optional.isPresent() && this.getPoiManager().exists(blockposition1, com.google.common.base.Predicates.alwaysTrue())) {
++                        this.getPoiManager().remove(blockposition1);
++                    }
++                    // Paper end
+                     this.getPoiManager().add(blockposition1, villageplacetype);
+                     DebugPackets.sendPoiAddedPacket(this, blockposition1);
+                 });