Update speechbrain.pretrained to speechbrain.inference

The new speechbrain v1.0.0 caused a breaking change which the proposed change aims to fix.
The `"pretrained"` module no longer exists. Instead, it is replaced by the `"inference"` method. Link to the issue: https://github.com/speechbrain/speechbrain/issues/2472

The second change removes the first slash character in the source parameter on line 40 to ensure Tacotron2 fetches from the online repo instead of locally.

README.md

@@ -33,11 +33,11 @@ pip install speechbrain
 
 ```
 import torchaudio
-from speechbrain.pretrained import Tacotron2
-from speechbrain.pretrained import HIFIGAN
+from speechbrain.inference import Tacotron2
+from speechbrain.inference import HIFIGAN
 
 # Intialize TTS (tacotron2) and Vocoder (HiFIGAN)
-tacotron2 = Tacotron2.from_hparams(source="/Sunbird/sunbird-lug-tts", savedir="tmpdir_tts")
+tacotron2 = Tacotron2.from_hparams(source="Sunbird/sunbird-lug-tts", savedir="tmpdir_tts")
 hifi_gan = HIFIGAN.from_hparams(source="speechbrain/tts-hifigan-ljspeech", savedir="tmpdir_vocoder")
 
 # Running the TTS