docs: correct vault backend path

Based on my testing with the guide above,
the original value in the sample code here:
`VAULT_BACKEND_PATH: rook/ver1`
...did not work and resulted in
a Vault path error when Rook attempted
to provision the OSD filesystem.
When I simplified it to:
`VAULT_BACKEND_PATH: rook`
... then it worked.

I also took the opportunity to add
a comment/clarification about the `VAULT_ADDR` URL.

Co-authored-by: Shahak Nagiel <snagiel@yahoo.com>
Signed-off-by: parth-gr <paarora@redhat.com>

Documentation/ceph-kms.md

@@ -144,12 +144,14 @@ security:
     connectionDetails:
         KMS_PROVIDER: vault
         VAULT_ADDR: https://vault.default.svc.cluster.local:8200
-        VAULT_BACKEND_PATH: rook/ver1
+        VAULT_BACKEND_PATH: rook
         VAULT_SECRET_ENGINE: kv
         VAULT_AUTH_METHOD: kubernetes
         VAULT_AUTH_KUBERNETES_ROLE: rook-ceph
 ```
 
+> Note: The `VAULT_ADDR` value above assumes that Vault is accessible within the cluster itself on the default port (8200). If running elsewhere, please update the URL accordingly.
+
 ### General Vault configuration
 
 As part of the token, here is an example of a policy that can be used: