Change LoginInboundConnection queue type to something that is actually thread-safe

proxy/src/main/java/com/velocitypowered/proxy/connection/client/LoginInboundConnection.java

@@ -30,9 +30,9 @@ import io.netty.buffer.ByteBufUtil;
 import io.netty.buffer.Unpooled;
 import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
 import java.net.InetSocketAddress;
-import java.util.ArrayDeque;
 import java.util.Optional;
 import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
 import net.kyori.adventure.text.Component;
 import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
@@ -58,7 +58,7 @@ public class LoginInboundConnection implements LoginPhaseConnection, KeyIdentifi
       InitialInboundConnection delegate) {
     this.delegate = delegate;
     this.outstandingResponses = Int2ObjectSyncMap.hashmap();
-    this.loginMessagesToSend = new ArrayDeque<>();
+    this.loginMessagesToSend = new ConcurrentLinkedQueue<>();
   }
 
   @Override