Remove leadFix rule

It's been fixed for ages, and the only code we still add is already in vanilla

src/main/java/carpet/CarpetSettings.java

@@ -864,13 +864,6 @@ public class CarpetSettings
     @Rule(desc = "fixes block placement rotation issue when player rotates quickly while placing blocks", category = RuleCategory.BUGFIX)
     public static boolean placementRotationFix = false;
 
-    @Rule(
-            desc = "Fixes leads breaking/becoming invisible in unloaded chunks",
-            extra = "You may still get visibly broken leash links on the client side, but server side the link is still there.",
-            category = RuleCategory.BUGFIX
-    )// needs checkfix for 1.15
-    public static boolean leadFix = false;
-
     @Rule(desc = "Spawning requires much less CPU and Memory", category = OPTIMIZATION)
     public static boolean lagFreeSpawning = false;
 

src/main/java/carpet/mixins/ServerEntity_leashFixMixin.java

@@ -1,34 +0,0 @@
-package carpet.mixins;
-
-import carpet.CarpetSettings;
-import org.spongepowered.asm.mixin.Final;
-import org.spongepowered.asm.mixin.Mixin;
-import org.spongepowered.asm.mixin.Shadow;
-import org.spongepowered.asm.mixin.injection.At;
-import org.spongepowered.asm.mixin.injection.Inject;
-import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
-
-import java.util.function.Consumer;
-import net.minecraft.network.protocol.Packet;
-import net.minecraft.network.protocol.game.ClientboundSetEntityLinkPacket;
-import net.minecraft.server.level.ServerEntity;
-import net.minecraft.world.entity.Entity;
-import net.minecraft.world.entity.Mob;
-
-@Mixin(ServerEntity.class)
-public class ServerEntity_leashFixMixin
-{
-    @Shadow @Final private Entity entity;
-
-    @Inject(method = "sendPairingData", at = @At("RETURN"))
-    private void sendLeashPackets(Consumer<Packet<?>> consumer_1, CallbackInfo ci)
-    {
-        if (CarpetSettings.leadFix)
-        {
-            if (entity instanceof Mob)
-            {
-                consumer_1.accept( new ClientboundSetEntityLinkPacket(entity, ((Mob) entity).getLeashHolder()));
-            }
-        }
-    }
-}

src/main/resources/carpet.mixins.json

@@ -54,7 +54,6 @@
     "ThreadedLevelLightEngine_scarpetChunkCreationMixin",
     "LivingEntity_cleanLogsMixin",
     "MobMixin",
-    "ServerEntity_leashFixMixin",
     "Villager_aiMixin",
     "Player_fakePlayersMixin",
     "ServerGamePacketListenerImpl_coreMixin",