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/manual.py

@@ -18,7 +18,7 @@ import logging
 import copy
 import re
 
-from api.db import ParserType
+from common.constants import ParserType
 from io import BytesIO
 from rag.nlp import rag_tokenizer, tokenize, tokenize_table, bullets_category, title_frequency, tokenize_chunks, docx_question_level
 from common.token_utils import num_tokens_from_string