chore: remove unsed code

component/dialer/dialer.go

@@ -17,9 +17,7 @@ var (
 	actualSingleStackDialContext = serialSingleStackDialContext
 	actualDualStackDialContext   = serialDualStackDialContext
 	tcpConcurrent                = false
-	DisableIPv6                  = false
 	ErrorInvalidedNetworkStack   = errors.New("invalided network stack")
-	ErrorDisableIPv6             = errors.New("IPv6 is disabled, dialer cancel")
 	ErrorConnTimeout             = errors.New("connect timeout")
 )
 
@@ -113,10 +111,6 @@ func dialContext(ctx context.Context, network string, destination netip.Addr, po
 		bindMarkToDialer(opt.routingMark, dialer, network, destination)
 	}
 
-	if DisableIPv6 && destination.Is6() {
-		return nil, ErrorDisableIPv6
-	}
-
 	address := net.JoinHostPort(destination.String(), port)
 	if opt.tfo {
 		return dialTFO(ctx, *dialer, network, address)
@@ -296,7 +290,7 @@ type dialResult struct {
 	isPrimary bool
 }
 
-func parseAddr(ctx context.Context,  network,address string, preferResolver resolver.Resolver) ([]netip.Addr, string, error) {
+func parseAddr(ctx context.Context, network, address string, preferResolver resolver.Resolver) ([]netip.Addr, string, error) {
 	host, port, err := net.SplitHostPort(address)
 	if err != nil {
 		return nil, "-1", err