Update prompt-design.md

Author: lpellegro

AI_CookBook/docs/prompt-design.md

@@ -560,7 +560,7 @@ There is no single way to create an execution graph. A JSON schema can be design
 ![JSON Nodes](assets/prompt-design/nodes.png)
 
 <div style="background: white; padding: 10px; display: inline-block;">
-  <img src="[diagram.png](https://webexsamples.github.io/webex-ai-agents/assets/prompt-design/nodes.png)" width="500">
+  <img src="https://webexsamples.github.io/webex-ai-agents/assets/prompt-design/nodes.png" width="500">
 </div>
 
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