Cross scene reference warning

How do I disable the Cross scene reference warning?

#if UNITY_EDITOR
using UnityEngine;
[ExecuteAlways]
public class UpdateMonoCamera : MonoBehaviour
{
    //updates player ECS camera in editor.
    [SerializeField] MonoCameraTag cameraTag;
    PlayerAuthoring player;
    private void Update()
    {
        if (Application.isPlaying == false)
        {

            if (player == null)
            {
                player = GameObject.FindFirstObjectByType<PlayerAuthoring>();
            }


            if (cameraTag && player)
            {
                cameraTag.transform.position = player.EditorGetPlayerCameraTransform().position;
                cameraTag.transform.rotation = player.EditorGetPlayerCameraTransform().rotation;
            }
        }
    }
}
#endif

Make the field private.