dillon1000/react

Fix: Don't read primaryChild.childExpirationTime (#18457)

This is a variant of the fix in 5a0f1d. We can't rely on the primary
fiber's `childExpirationTime` field to be correct.

In this case, we can read from the Suspense boundary fiber instead.
This will include updates that exist in the fallback fiber, but that's
not a big deal; the important thing is that we don't drop updates.