docs: Node version file: Clarify effect of version range in engines.node

**Description:**
In `docs/advanced-usage.md#node-version-file`, explain what effect `"engines": { "node": ">=16.0.0" }` would have had if it was not overridden by the volta option.

**Justification:**
I cannot tell from reading whether the example would install node 16, 20, 21 or 22.

**Are you willing to submit a PR?**
Yes.