docs: clarify load parent() behaviour (#12655)

closes #12654

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Co-authored-by: Simon H <[email protected]>

Author: bleucitron

documentation/docs/20-core-concepts/20-load.md

@@ -664,6 +664,7 @@ To summarize, a `load` function will rerun in the following situations:
 - It references a property of `url` (such as `url.pathname` or `url.search`) whose value has changed. Properties in `request.url` are _not_ tracked
 - It calls `url.searchParams.get(...)`, `url.searchParams.getAll(...)` or `url.searchParams.has(...)` and the parameter in question changes. Accessing other properties of `url.searchParams` will have the same effect as accessing `url.search`.
 - It calls `await parent()` and a parent `load` function reran
+- A child `load` function calls `await parent()` and is rerunning, and the parent is a server load function
 - It declared a dependency on a specific URL via [`fetch`](#making-fetch-requests) (universal load only) or [`depends`](types#public-types-loadevent), and that URL was marked invalid with [`invalidate(url)`](modules#$app-navigation-invalidate)
 - All active `load` functions were forcibly rerun with [`invalidateAll()`](modules#$app-navigation-invalidateall)