cmd/tailscale/cli: make update visible in list (tailscale#8662)

This also makes "HIDDEN: " work (requires the custom UsageFunc).

Updates tailscale#6995

Signed-off-by: Chris Palmer <cpalmer@tailscale.com>
Signed-off-by: Alex Paguis <alex@windscribe.com>

cmd/tailscale/cli/cli.go

@@ -130,6 +130,7 @@ change in the future.
 			netlockCmd,
 			licensesCmd,
 			exitNodeCmd,
+			updateCmd,
 		},
 		FlagSet:   rootfs,
 		Exec:      func(context.Context, []string) error { return flag.ErrHelp },
@@ -145,8 +146,6 @@ change in the future.
 	switch {
 	case slices.Contains(args, "debug"):
 		rootCmd.Subcommands = append(rootCmd.Subcommands, debugCmd)
-	case slices.Contains(args, "update"):
-		rootCmd.Subcommands = append(rootCmd.Subcommands, updateCmd)
 	}
 	if runtime.GOOS == "linux" && distro.Get() == distro.Synology {
 		rootCmd.Subcommands = append(rootCmd.Subcommands, configureHostCmd)