refactor code (#583)

### What problem does this PR solve?

### Type of change

- [x] Refactoring

deepdoc/parser/ppt_parser.py

@@ -14,7 +14,7 @@ from io import BytesIO
 from pptx import Presentation
 
 
-class HuPptParser(object):
+class RAGFlowPptParser(object):
     def __init__(self):
         super().__init__()