Enable the TAC in develop

While we work through fixing all the tests on matrix-org/matrix-react-sdk#12439 enable the TAC on nightly so we can get wider testing.

Author: dbkr

element.io/develop/config.json

@@ -48,6 +48,7 @@
     },
     "privacy_policy_url": "https://element.io/cookie-policy",
     "features": {
+        "threadsActivityCentre": true,
         "feature_video_rooms": true,
         "feature_new_room_decoration_ui": true,
         "feature_element_call_video_rooms": true