Update "pretrained name"

README.md

@@ -49,11 +49,11 @@ pip install nemo_toolkit['all']
 ```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