Update install-blob-csi-driver.md

Author: andyzhangx

docs/install-blob-csi-driver.md

@@ -1,6 +1,6 @@
 ## Install Azure Blob Storage CSI driver on a Kubernetes cluster
 
- - [install CSI driver master version](./install-csi-driver-master.md)
+ - [install CSI driver master version](./install-csi-driver-master.md) (only for testing purpose)
  - [install v1.15.0 CSI driver](./install-csi-driver-v1.15.0.md)
  - [install v1.14.0 CSI driver](./install-csi-driver-v1.14.0.md)
  - [install v1.13.0 CSI driver](./install-csi-driver-v1.13.0.md)