Update package.json to make extension description accurate (#653)

Description points to up-to-date information and removes old extension pack recommendations

Co-authored-by: Mariana Mihova <10135329+marianan@users.noreply.github.com>

package.json

@@ -1,7 +1,7 @@
 {
   "name": "azure-iot-edge",
   "displayName": "Azure IoT Edge",
-  "description": "This extension is now a part of Azure IoT Tools extension pack. We highly recommend installing Azure IoT Tools to get full capabilities for Azure IoT development. Develop, deploy, debug, and manage your IoT Edge solution.",
+  "description": "This extension is now in maintenance mode. See announcement https://github.com/microsoft/vscode-azure-iot-edge/issues/639#issue-1359146049 and latest documentation here: https://learn.microsoft.com/en-us/azure/iot-edge/how-to-vs-code-develop-module.",
   "version": "1.25.11",
   "publisher": "vsciot-vscode",
   "aiKey": "95b20d64-f54f-4de3-8ad5-165a75a6c6fe",