Auto merge of #24401 - gterzian:ensure_done_chan_is_none_when_revalidating, r=jdm

Fetch: ensure consistency between response, done-chan, and cache state.

This ensures that when a cached response is not used because it requires revalidation, the done chan is set back to `None`(since the cache might have set it to `Some` when constructing the response requiring revalidation).

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- [ ] These changes fix #24399 (GitHub issue number if applicable)

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