Add line breaks to flowchart labels in README

Updated the flowchart in the README to include line breaks in the labels.

https://github.com/microsoft/Web-Dev-For-Beginners/blob/main/translations/ja/1-getting-started-lessons/1-intro-to-programming-languages/README.md

#PingMSFTDocs

translations/ja/1-getting-started-lessons/1-intro-to-programming-languages/README.md

@@ -465,7 +465,7 @@ switch (dayOfWeek) {
 **自信をちょっと高めるアップデート：**  
 ```mermaid
 flowchart LR
-    A["📝 文[命令]"] --> B["📦 変数[記憶域]"] --> C["🔀 制御フロー[判断]"] --> D["🎉 動作するプログラム!"]
+    A["📝 文<br/>[命令]"] --> B["📦 変数<br/>[記憶域]"] --> C["🔀 制御フロー<br/>[判断]"] --> D["🎉 動作するプログラム!"]
     
     style A fill:#ffeb3b
     style B fill:#4caf50