Fix classify text tutorial

Change-Id: Ib86df7cf37588b7a7fc0c7f4ad4fc70548152354

Author: Jon Wayne Parrott

language/classify_text/classify_text_tutorial.py

@@ -89,8 +89,8 @@ def index(path, index_file):
         except Exception:
             print('Failed to process {}'.format(file_path))
 
-    with io.open(index_file, 'w') as f:
-        f.write(json.dumps(result).encode('utf-8'))
+    with io.open(index_file, 'w', encoding='utf-8') as f:
+        f.write(json.dumps(result))
 
     print('Texts indexed in file: {}'.format(index_file))
     return result