Merge pull request #44 from microsoft/fix-lesson32-videourl

Update RAG explainer video link in documentation

Author: elbruno

03-CoreGenerativeAITechniques/02-retrieval-augmented-generation.md

@@ -4,7 +4,7 @@ In this lesson learn how to use **Retrieval-Augmented Generation (RAG)** in your
 
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-[![RAG explainer video](https://img.youtube.com/vi/Av1FCQf83QU/0.jpg)](https://youtu.be/Av1FCQf83QU?feature=shared)
+[![RAG explainer video](https://img.youtube.com/vi/mY7O0OY2vho/0.jpg)](https://youtu.be/mY7O0OY2vho?feature=shared)
 
 _⬆️Click the image to watch the video⬆️_