Update pretrained name.

README.md

@@ -45,11 +45,11 @@ NOTE: In order to generate audio, you also need a spectrogram generator from NeM
 ```python
 # Load FastPitch
 from nemo.collections.tts.models import FastPitchModel
-spec_generator = FastPitchModel.from_pretrained("tts_en_fastpitch")
+spec_generator = FastPitchModel.from_pretrained("nvidia/tts_en_fastpitch")
 
 # Load vocoder
 from nemo.collections.tts.models import HifiGanModel
-model = HifiGanModel.from_pretrained(model_name="tts_hifigan")
+model = HifiGanModel.from_pretrained(model_name="nvidia/tts_hifigan")
 ```
 
 ### Generate audio