refactor(netx): the TimeoutDialer is useless (#366)

We already configure a timeout in the underlying dialer, hence
there's no point in keeping the TimeoutDialer around.

Part of https://github.com/ooni/probe/issues/1507

internal/engine/experiment/ndt7/dial.go

@@ -36,7 +36,6 @@ func (mgr dialManager) dialWithTestName(ctx context.Context, testName string) (*
 	var reso resolver.Resolver = resolver.SystemResolver{}
 	reso = resolver.LoggingResolver{Resolver: reso, Logger: mgr.logger}
 	var dlr dialer.Dialer = dialer.Default
-	dlr = dialer.TimeoutDialer{Dialer: dlr}
 	dlr = dialer.ErrorWrapperDialer{Dialer: dlr}
 	dlr = dialer.LoggingDialer{Dialer: dlr, Logger: mgr.logger}
 	dlr = dialer.DNSDialer{Dialer: dlr, Resolver: reso}