Fix secret key inconsistency cross the RAGFlow servers (#14591)

### What problem does this PR solve?

A and B, two API servers and a REDIS server.
If A and REDIS restart, B will hold the obsolete secret key and will
lead to error.

TODO:
app.config['SECRET_KEY'] and app.secret_key still hold obsolete secret
key.

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

---------

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

api/utils/api_utils.py

@@ -325,7 +325,7 @@ def token_required(func):
         from common import settings
         from itsdangerous.url_safe import URLSafeTimedSerializer as Serializer
         try:
-            jwt = Serializer(secret_key=settings.SECRET_KEY)
+            jwt = Serializer(secret_key=settings.get_secret_key())
             raw_token = str(jwt.loads(token))
             user = UserService.query(access_token=raw_token, status=StatusEnum.VALID.value)
             if user: