doc(preload): Update Exposure Notification app meta data

preload/apps/exnostat/metadata.json

-{"author": "schneider", "name": "Exposure Notification Counter", "description": "Count exposure notifications received via BLE", "category": "Hardware", "revision": 1, "source":"preload"}
+{"author": "schneider", "name": "Exposure Notification Stats", "description": "Count Exposure Notifications received via BLE", "category": "Hardware", "revision": 1, "source":"preload"}