fix redis pvc in helm deployment
### What problem does this PR solve?
_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
### What problem does this PR solve?
Add's a Helm chart for deploying RAGFlow on Kubernetes.
Closes#864.
### Type of change
- [X] New Feature (non-breaking change which adds functionality)
