clientupdate: mention release track when running latest (#10039)

Not all users know about our tracks and versioning scheme. They can be
confused when e.g. 1.52.0 is out but 1.53.0 is available. Or when 1.52.0
is our but 1.53 has not been built yet and user is on 1.51.x.

Updates #cleanup

Signed-off-by: Andrew Lytvynov <awly@tailscale.com>

clientupdate/clientupdate.go

@@ -237,10 +237,10 @@ func Update(args Arguments) error {
 func (up *Updater) confirm(ver string) bool {
 	switch cmpver.Compare(version.Short(), ver) {
 	case 0:
-		up.Logf("already running %v; no update needed", ver)
+		up.Logf("already running %v version %v; no update needed", up.track, ver)
 		return false
 	case 1:
-		up.Logf("installed version %v is newer than the latest available version %v; no update needed", version.Short(), ver)
+		up.Logf("installed %v version %v is newer than the latest available version %v; no update needed", up.track, version.Short(), ver)
 		return false
 	}
 	if up.Confirm != nil {