How delete object in one side at bidirectional relation?

You can achieve this more simply by doing the below:

public void deletePlayerFromTeam(int idPlayer){
    Player player = //loadPlayer;
    player.setTeam(null);

    playerRepository.save(player);
}

You can also achieve this in your original code by setting the player.team to null and and by setting cascade on the collection to merge:

@OneToMany(mappedBy = "team", fetch = FetchType.LAZY, cascade = CascadeType.MERGE)
private List<Player> playerList;

You should always ensure both sides of the relationship are maintained consistently.