fix missing model choice, test=doc

paddlespeech/t2s/exps/synthesize_e2e.py

@@ -284,7 +284,8 @@ def main():
         default='fastspeech2_csmsc',
         choices=[
             'speedyspeech_csmsc', 'speedyspeech_aishell3', 'fastspeech2_csmsc',
-            'fastspeech2_ljspeech', 'fastspeech2_aishell3', 'fastspeech2_vctk'
+            'fastspeech2_ljspeech', 'fastspeech2_aishell3', 'fastspeech2_vctk',
+            'tacotron2_csmsc'
         ],
         help='Choose acoustic model type of tts task.')
     parser.add_argument(