Values 的合并策略
Deleting a default key | https://helm.sh/docs/chart_template_guide/values_files/#deleting-a-default-key
If you need to delete a key from the default values, you may override the value of the key to be
null, in which case Helm will remove the key from the overridden values merge.
null, in which case Helm will remove the key from the overridden values merge.