remove the useless model architecture

video_prediction_tools/model_modules/model_architectures.py

 def known_models():
     """
     An auxilary function
-    ours_vae_l1 and ours_gan are from savp papers
     :return: dictionary of known model architectures
     """
     model_mappings = {
-        'ground_truth': 'GroundTruthVideoPredictionModel',
-        'savp': 'SAVPVideoPredictionModel',
         'convLSTM': 'VanillaConvLstmVideoPredictionModel',
         'convLSTM_gan': "ConvLstmGANVideoPredictionModel",
         'weatherBench': 'WeatherBenchModel'