tests: fix up activity collision test

test/web/activity_pub/activity_pub_test.exs

@@ -140,7 +140,7 @@ test "returns the activity if one with the same id is already in" do
       activity = insert(:note_activity)
       {:ok, new_activity} = ActivityPub.insert(activity.data)
 
-      assert activity == new_activity
+      assert activity.id == new_activity.id
     end
 
     test "inserts a given map into the activity database, giving it an id if it has none." do