Replaced redis with Valkey (#3164)

### What problem does this PR solve?

Replaced redis with Valkey. Close #3070

### Type of change

- [ ] Bug Fix (non-breaking change which fixes an issue)
- [ ] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [x] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

rag/utils/redis_conn.py

@@ -1,6 +1,6 @@
 import json
 
-import redis
+import valkey as redis
 import logging
 from rag import settings
 from rag.utils import singleton
@@ -40,7 +40,7 @@ class RedisDB:
                                      db=int(self.config.get("db", 1)),
                                      password=self.config.get("password"),
                                      decode_responses=True)
-        except Exception as e:
+        except Exception:
             logging.warning("Redis can't be connected.")
         return self.REDIS