all: use math/rand/v2 more

Updates #11058

Signed-off-by: Maisem Ali <maisem@tailscale.com>

cmd/sniproxy/handlers.go

@@ -7,7 +7,7 @@ import (
 	"context"
 	"fmt"
 	"log"
-	"math/rand"
+	"math/rand/v2"
 	"net"
 	"net/netip"
 	"slices"
@@ -47,7 +47,7 @@ func (h *tcpRoundRobinHandler) Handle(c net.Conn) {
 		return netutil.NewOneConnListener(c, nil), nil
 	}
 
-	dest := h.To[rand.Intn(len(h.To))]
+	dest := h.To[rand.IntN(len(h.To))]
 	dial := &tcpproxy.DialProxy{
 		Addr:        fmt.Sprintf("%s:%s", dest, port),
 		DialContext: h.DialContext,