fix: use consistent telemetryUrl default in master.follower (#7809)

Update telemetryUrl to use the same default value as the master command
for consistency and maintainability.

Addresses review feedback from PR #7808

weed/command/master_follower.go

@@ -42,7 +42,7 @@ func init() {
 	mf.metricsIntervalSec = aws.Int(0)
 	mf.raftResumeState = aws.Bool(false)
 	mf.maxParallelVacuumPerServer = aws.Int(1)
-	mf.telemetryUrl = aws.String("")
+	mf.telemetryUrl = aws.String("https://telemetry.seaweedfs.com/api/collect")
 	mf.telemetryEnabled = aws.Bool(false)
 }