Add msc4429_enabled to Complement tests

docker/complement/conf/workers-shared-extra.yaml.j2

@@ -143,6 +143,8 @@ experimental_features:
   msc4354_enabled: true
   # `/sync` `state_after`
   msc4222_enabled: true
+  # Profile updates down legacy /sync
+  msc4429_enabled: true
 
 server_notices:
   system_mxid_localpart: _server