Some teams still own some workers. Workers have been used to accelerate building sites, but the last update removed this deprecated option.
Today, we are refunding all workers. All workers will be removed from all teams, and for each worker removed this way, owners get 1 million K$, as this amount exactly equals what a worker did before. You will find an entry in your transaction log later today and your workers will be gone. No action is required on your side.