h-a: zigbee2m: Add dialout supplemental group

Zigbee2MQTT needs to be able to read and write to the serial device for
the ConBee II USB controller.  I'm not exactly sure what changed, or how
it was able to access it before the recent update.

The _dialout_ group has GID 18 on Fedora.

home-assistant/zigbee2mqtt.yaml

@@ -93,6 +93,8 @@ spec:
           name: zigbee-device
       securityContext:
         fsGroup: 302
+        supplementalGroups:
+        - 18
       volumes:
       - name: zigbee2mqtt-data
         persistentVolumeClaim: