Kibana error [ FATAL Error: [config validation of [elasticsearch].username]: value of "elastic" is forbidden.]

Elastic Stack Kibana
4

I have a similar situation here. On startup Kibana says

FATAL Error: [config validation of [elasticsearch].username]: value of "elastic" is forbidden. This is a superuser account that cannot write to system indices that Kibana needs to function. Use a service account token instead. Learn more: https://www.elastic.co/guide/en/elasticsearch/reference/8.0/service-accounts.html

Strangely however, this value is not defined in kibana.yml:

$ grep username config/kibana.yml
# the username and password that the Kibana server uses to perform maintenance on the Kibana
#elasticsearch.username: ${elasticsearch.username}

Instead I'm using a service token:

#elasticsearch.username: ${elasticsearch.username}
#elasticsearch.password: ${elasticsearch.password}
elasticsearch.serviceAccountToken: "edited"

After creating the token I got this result

{
  "created" : true,
  "token" : {
    "name" : "token_E1iT534Bm30JRve8bsYA",
    "value" : "edited"
  }
}

I ran a test request

curl -H "Authorization: Bearer edited" https://hostname -f:9200/_security/_authenticate?pretty

and got

{
  "username" : "elastic/kibana",
  "roles" : [ ],
  "full_name" : "Service account - elastic/kibana",
  "email" : null,
  "token" : {
    "name" : "token_E1iT534Bm30JRve8bsYA",
    "type" : "_service_account_index"
  },
  "metadata" : {
    "_elastic_service_account" : true
  },
  "enabled" : true,
  "authentication_realm" : {
    "name" : "_service_account",
    "type" : "_service_account"
  },
  "lookup_realm" : {
    "name" : "_service_account",
    "type" : "_service_account"
  },
  "authentication_type" : "token"
}