Bad use of YAML document start (`---`) in examples

[lindhe]

I've seen that the YAML document start marker (---) is sometimes placed at the end of YAML documents in the examples:

https://github.com/helm/helm-www/blob/3e2a35f2e91f3529543bb8faca463ba5d6be9df8/content/en/docs/chart_template_guide/variables.md?plain=1#L149C1-L149C4

I have seen this mislead people to believe that this marker should be there even when there's only a single document:

like: this
---

I think it would be better if our examples consistently used --- as it is intended to be used – exclusively at the start of new documents (and optionally omitted when there's only a single document).