The value in this JSON is a number type, but
Your openHAB Thing Channel (and your Item) is a String type. What happens if you change your Channel and Item types to a Number?
Another issue might be that the Things file isn’t loading properly. You could restart openHAB to fix that, or do this.
No you don’t need the Zigbee binding, just the V2 MQTT binding.
EDIT:
Actually, can you check your topic? In your JSON extract you say the topic is:
/tele/CONTACT_BUREAU_PORTE/SENSOR
but in your openHAB config you use the topic
tele/CONTACT_BUREAU_PORTE/SENSOR
Note the first slash is missing.
I have just setup a test thing by copy/pasting your config for Porte Bureau, and sent your JSON string to
tele/CONTACT_BUREAU_PORTE/SENSOR
And the Item updates correctly - so there is no need to change the Channel and Item to a Number type. As long as the Topics are correct (and your Broker Thing (mqtt:broker:MQTTBroker) is correctly configured to connect to your MQTT broker) your configuration should work.