Update main config json as stable diffusion 2.1 has been removed

main_config.json

@@ -1 +1 @@
-{"text_encoder_name": "google/flan-t5-large", "scheduler_name": "stabilityai/stable-diffusion-2-1", "unet_model_name": null, "unet_model_config_path": "configs/diffusion_model_config.json", "snr_gamma": 5.0}
+{"text_encoder_name": "google/flan-t5-large", "scheduler_name": "sd2-community/stable-diffusion-2-1", "unet_model_name": null, "unet_model_config_path": "configs/diffusion_model_config.json", "snr_gamma": 5.0}