cmd/sketch: only show structured logs printf if --unsafe

The inner sketch binary running in docker runs with --unsafe.
diff --git a/cmd/sketch/main.go b/cmd/sketch/main.go
index 1af73f0..5134802 100644
--- a/cmd/sketch/main.go
+++ b/cmd/sketch/main.go
@@ -87,7 +87,9 @@
 		if err != nil {
 			return fmt.Errorf("cannot create log file: %v", err)
 		}
-		fmt.Printf("structured logs: %v\n", logFile.Name())
+		if *unsafe {
+			fmt.Printf("structured logs: %v\n", logFile.Name())
+		}
 		defer logFile.Close()
 		slogHandler = slog.NewJSONHandler(logFile, &slog.HandlerOptions{Level: slog.LevelDebug})
 		slogHandler = skribe.AttrsWrap(slogHandler)