Update custom-tools.mdx

Author: sahilsuman933

fern/tools/custom-tools.mdx

@@ -139,7 +139,7 @@ By following these guidelines and adapting the sample payload, you can easily co
 
 **Video Tutorial:**
 <iframe
-        src="https://www.youtube.com/embed/4fLe3sRH_uI?si=rAE5sWS2f8Ky5Zgx"
+        src="https://www.youtube.com/embed/APnRljus0qg?si=5EQ4PaAconJYNona"
         title="YouTube video player"
         frameborder="0"
         allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share"