fix(mempool): use no-op mempool as default (backport #19970) (#20008)

Co-authored-by: Tom <54514587+GAtom22@users.noreply.github.com>
Co-authored-by: marbar3778 <marbar3778@yahoo.com>
Co-authored-by: Julien Robert <julien@rbrt.fr>

server/config/config.go

@@ -263,7 +263,7 @@ func DefaultConfig() *Config {
 			},
 		},
 		Mempool: MempoolConfig{
-			MaxTxs: 5_000,
+			MaxTxs: -1,
 		},
 	}
 }

server/config/toml.go

@@ -240,7 +240,7 @@ stop-node-on-err = {{ .Streaming.ABCI.StopNodeOnErr }}
 
 [mempool]
 # Setting max-txs to 0 will allow for a unbounded amount of transactions in the mempool.
-# Setting max_txs to negative 1 (-1) will disable transactions from being inserted into the mempool.
+# Setting max_txs to negative 1 (-1) will disable transactions from being inserted into the mempool (no-op mempool).
 # Setting max_txs to a positive number (> 0) will limit the number of transactions in the mempool, by the specified amount.
 #
 # Note, this configuration only applies to SDK built-in app-side mempool