fix: Include name key in example of imagePullSecrets

When `.Values.image.imagePullSecrets` was introduced in #174, we opted
to use the same format for `imagePullSecrets` list as used in
Kubernetes' PodSpec; it's a list of objects that requires each list
element to have the key `name`.
We failed to indicate this in the example given in the comment.
This change fixes that.

Author: lindhe

charts/invenio/values.yaml

@@ -33,7 +33,7 @@ image:
   ## ref: https://kubernetes.io/docs/tasks/configure-pod-container/pull-image-private-registry/
   ## e.g:
   ## pullSecrets:
-  ##   - myRegistryKeySecretName
+  ##   - name: myRegistryKeySecretName
   ##
   pullSecrets: []