Trainer.model.push_to_hub() does not allow a private repository flag

### System Info As the title described. ### Who can help? _No response_ ### Information - [ ] The official example scripts - [ ] My own modified scripts ### Tasks - [ ] An officially supported task in the `examples` folder (such as GLUE/SQuAD, ...) - [ ] My own task or dataset (give details below) ### Reproduction Use the function Trainer.model.push_to_hub(). ### Expected behavior Trainer.model.push_to_hub() allows a private repository flag.