fix unexpected indent

Author: supotato6

paddlex/inference/pipelines/text_to_speech/pipeline.py

@@ -87,7 +87,7 @@ def predict(
         Returns:
             PwganResult: The predicted pwgan results, support str and json output.
         """
-            sentences = [] 
+        sentences = [] 
         if isinstance(input, str):
             if input.endswith(".txt"):
                 if not os.path.exists(input):