fix(xtts_manager): name_to_id() should return dict

This is how the other embedding managers work

TTS/tts/layers/xtts/xtts_manager.py

@@ -7,7 +7,7 @@ def __init__(self, speaker_file_path=None):
 
     @property
     def name_to_id(self):
-        return self.speakers.keys()
+        return self.speakers
 
     @property
     def num_speakers(self):