fix: update persistence reference

Signed-off-by: Roberto Utagawa <[email protected]>

Author: Roberto-Utagawa

charts/grafana/values.yaml

@@ -411,7 +411,7 @@ extraContainerVolumes: []
 #    emptyDir: {}
 
 ## Enable persistence using Persistent Volume Claims
-## ref: https://kubernetes.io/docs/user-guide/persistent-volumes/
+## ref: https://kubernetes.io/docs/concepts/storage/persistent-volumes/
 ##
 persistence:
   type: pvc