> mapRelay (used to relay announced transactions that are no longer in the mempool) doesn't have an absolute memory limit, only an implicit one based on the rate of transaction announcements.
> Remove it.
Note that we can't remove a transaction from the mempool with a replacement transaction, as the `sendrawtransaction(tx_b)` RPC would fail with `txn-mempool-conflict`, but as of D15279 we can use avalanche to reject a tx from the mempool.
This is a backport of core#27625
Depends on D18366