refactor(netxlite): add Transport suffix to DNS transports (#731)

This diff has been extracted from c2f7ccab0e

See https://github.com/ooni/probe/issues/2096

internal/engine/experiment/webstepsx/th.go

@@ -368,5 +368,5 @@ const thResolverURL = "https://dns.google/dns-query"
 // Here we're using github.com/apex/log as the logger, which
 // is fine because this is backend only code.
 var thResolver = netxlite.WrapResolver(log.Log, netxlite.NewSerialResolver(
-	netxlite.NewDNSOverHTTPS(http.DefaultClient, thResolverURL),
+	netxlite.NewDNSOverHTTPSTransport(http.DefaultClient, thResolverURL),
 ))