Conflict notifications fail to compute the PR number with merge queues

[ehuss]

The conflict notification tries to determine which PR caused the conflict. However, with merge queues, it seems to be failing to do this:

rust-lang/reference#1664 (comment) is an example.
It should be able to see that rust-lang/reference@06994b6 is rust-lang/reference#1696.

The code for this is here:

triagebot/src/handlers/merge_conflicts.rs

Lines 169 to 179 in 0400514

	// Make a guess as to what is responsible for the conflict. This is only a
	// guess, it can be inaccurate due to many factors (races, rebases, force
	// pushes, etc.).
	let possibly = match repo.pulls_for_commit(gh, push_sha).await {
	Ok(prs) if prs.len() == 1 => Some(format!("#{}", prs[0].number)),
	Err(e) => {
	log::warn!("could not determine PRs for {push_sha}: {e:?}");
	None
	}
	_ => None,
	}

I'm wondering if there is a race on the GitHub side, where it computes this information async, and the information is not yet available?