Remove unused entity remapper.

proxy/src/main/java/com.velocitypowered/proxy/protocol/remap/Minecraft18EntityIdRemapper.java

@@ -1,40 +0,0 @@
-package com.velocitypowered.proxy.protocol.remap;
-
-import com.velocitypowered.proxy.protocol.ProtocolConstants;
-import io.netty.buffer.ByteBuf;
-
-public class Minecraft18EntityIdRemapper implements EntityIdRemapper {
-    private final int clientId;
-    private int serverId;
-
-    public Minecraft18EntityIdRemapper(int clientId, int serverId) {
-        this.clientId = clientId;
-        this.serverId = serverId;
-    }
-
-    @Override
-    public ByteBuf remap(ByteBuf original, ProtocolConstants.Direction direction) {
-        if (clientId == serverId) {
-            // If these are equal (i.e. first connection), no remapping is required.
-            return original.retain();
-        }
-
-        // TODO: Implement.
-        throw new UnsupportedOperationException("1.8 doesn't allow switching servers.");
-    }
-
-    @Override
-    public int getClientEntityId() {
-        return clientId;
-    }
-
-    @Override
-    public int getServerEntityId() {
-        return serverId;
-    }
-
-    @Override
-    public void setServerEntityId(int id) {
-        this.serverId = id;
-    }
-}