Update bing.md

Author: aslan-im

docs/tutorials/web-search/bing.md

@@ -6,6 +6,9 @@ title: "Bing"
 :::warning
 This tutorial is a community contribution and is not supported by the Open WebUI team. It serves only as a demonstration on how to customize Open WebUI for your specific use case. Want to contribute? Check out the contributing tutorial.
 :::
+:::warning
+Bing Search APIs will be retired on 11th August 2025. New deployments are not supported.
+:::
 
 ## Bing API