mempoolfullrbf=1 behaviour has been the default since v28 and the argument has
been removed since v29 subsequently. The getmempoolinfo RPC stops returning the
deprecated fullrbf key in the response unless the user requests it via the
-deprecatedrpc=fullrbf node argument.
Also, the bip125-replaceable key is removed from the mempool RPCs
responses (because it, too, has been deprecated since v29) unless the user
requests it via -deprecatedrpc=bip125 node argument. Affected mempool RPCs
are getrawmempool, getmempoolancestors, getmempooldescendants, and
getmempoolentry.