Move some constants to common (#11004)

### What problem does this PR solve?

As title.

### Type of change

- [x] Refactoring

---------

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

rag/app/paper.py

@@ -19,7 +19,7 @@ import copy
 import re
 
 from deepdoc.parser.figure_parser import vision_figure_parser_pdf_wrapper
-from api.db import ParserType
+from common.constants import ParserType
 from rag.nlp import rag_tokenizer, tokenize, tokenize_table, add_positions, bullets_category, title_frequency, tokenize_chunks
 from deepdoc.parser import PdfParser, PlainParser
 import numpy as np