refactor(webconnectivity@v0.5): improve logging clarity (#964)

We're bumping the experiment's version number because we changed the name of the field used to contain late/duplicate DNS responses. We have also changed the algorithm to determine `#dnsDiff`. However, the change should only impact how we log this information. Overall, here the idea is to provide users with a reasonably clear explanation of how the probe maps observations to blocking and accessible using expected/unexpected as the conceptual framework.

Part of https://github.com/ooni/probe/issues/2237

internal/experiment/webconnectivity/dnsresolvers.go

@@ -268,9 +268,6 @@ func (t *DNSResolvers) waitForLateReplies(parentCtx context.Context, trace *meas
 	defer t.WaitGroup.Done()
 	const lateTimeout = 500 * time.Millisecond
 	events := trace.DelayedDNSResponseWithTimeout(parentCtx, lateTimeout)
-	if length := len(events); length > 0 {
-		t.Logger.Warnf("got %d late DNS replies", length)
-	}
 	t.TestKeys.AppendDNSLateReplies(events...)
 }