instance actor: drop updated field

static/instance-actor.as2.json

@@ -8,7 +8,6 @@
   "url": "https://fed.brid.gy/",
   "preferredUsername": "fed.brid.gy",
   "summary": "Bridging the new social internet",
-  "updated": "2023-12-26T16:53:48.598945+00:00",
   "name": "Bridgy Fed",
   "attachment": [{
     "name": "Web site",