[`Refactor`] `save_model_card` function in `text_to_image` examples (#7051)
* Refactor save_model_card function to handle images and repo_folder parameters
* Discard changes to examples/text_to_image/train_text_to_image.py
* Discard changes to examples/text_to_image/train_text_to_image_lora_sdxl.py
* Update train_text_to_image_lora.py
* Update train_text_to_image_sdxl.py