chore: apply feedback on readme and vars

Signed-off-by: Devin Buhl <devin@buhl.casa>

bootstrap/vars/addons.sample.yaml

@@ -28,7 +28,7 @@ weave_gitops:
 # https://github.com/kubernetes-csi/csi-driver-nfs
 csi_driver_nfs:
   enabled: false
-  storage_class: []
+  storage_class:
     # - name:   # name of the storage class (must match [a-z0-9-]+)
     #   server: # dns name or ip address of nfs server
     #   share:  # exported share (path)