Update quick_start_cn.md (#3176)

docs/source/tts/quick_start_cn.md

@@ -87,8 +87,8 @@ checkpoint_name
 ├── snapshot_iter_*.pdz
 ├── speech_stats.npy
 ├── phone_id_map.txt
-├── spk_id_map.txt (optimal)
-└── tone_id_map.txt (optimal)
+├── spk_id_map.txt (optional)
+└── tone_id_map.txt (optional)
 ```
 **Vocoders:**
 ```text