Remove link to retired module

Author: dominicbetts

articles/iot-central/TOC.yml

@@ -25,8 +25,6 @@
         href: core/tutorial-connect-device.md
       - name: Create a device group
         href: core/tutorial-use-device-groups.md
-      - name: Connect an IoT Edge device
-        href: /training/modules/connect-iot-edge-device-to-iot-central/
       - name: Create a gateway device template
         href: core/tutorial-define-gateway-device-type.md
     - name: Extend your application