fix: typo in BucketUsageMetrics group registration in v3 metrics (#20090)

```
curl http://localhost:9000/minio/metrics/v3/cluster/usage/buckets
```

Did not work as documented, due to the fact that there was a typo
in the bucket usage metrics registration group. This endpoint is
a cluster endpoint and does not require any `buckets` argument.

cmd/metrics-v3-handler.go

@@ -163,7 +163,7 @@ func (h *metricsV3Server) handle(path string, isListingRequest bool, buckets []s
 		http.Error(w, "Metrics Resource Not found", http.StatusNotFound)
 	})
 
-	// Require that metrics path has at least component.
+	// Require that metrics path has one component at least.
 	if path == "/" {
 		return notFoundHandler
 	}