Remove -mempoolreplacement to prevent needless block prop slowness.

At this point there is no reasonable excuse to disable opt-in RBF,
and, unlike when this option was added, there are now significant
issues created when disabling it (in the form of compact block
reconstruction failures). Further, it breaks a lot of modern wallet
behavior.

test/functional/feature_rbf.py

@@ -64,7 +64,7 @@ def make_utxo(node, amount, confirmed=True, scriptPubKey=CScript([1])):
 
 class ReplaceByFeeTest(BitcoinTestFramework):
     def set_test_params(self):
-        self.num_nodes = 2
+        self.num_nodes = 1
         self.extra_args = [
             [
                 "-maxorphantx=1000",
@@ -74,9 +74,6 @@ class ReplaceByFeeTest(BitcoinTestFramework):
                 "-limitdescendantcount=200",
                 "-limitdescendantsize=101",
             ],
-            [
-                "-mempoolreplacement=0",
-            ],
         ]
 
     def skip_test_if_missing_module(self):
@@ -148,16 +145,12 @@ class ReplaceByFeeTest(BitcoinTestFramework):
 
         # This will raise an exception due to insufficient fee
         assert_raises_rpc_error(-26, "insufficient fee", self.nodes[0].sendrawtransaction, tx1b_hex, 0)
-        # This will raise an exception due to transaction replacement being disabled
-        assert_raises_rpc_error(-26, "txn-mempool-conflict", self.nodes[1].sendrawtransaction, tx1b_hex, 0)
 
         # Extra 0.1 BTC fee
         tx1b = CTransaction()
         tx1b.vin = [CTxIn(tx0_outpoint, nSequence=0)]
         tx1b.vout = [CTxOut(int(0.9 * COIN), CScript([b'b' * 35]))]
         tx1b_hex = txToHex(tx1b)
-        # Replacement still disabled even with "enough fee"
-        assert_raises_rpc_error(-26, "txn-mempool-conflict", self.nodes[1].sendrawtransaction, tx1b_hex, 0)
         # Works when enabled
         tx1b_txid = self.nodes[0].sendrawtransaction(tx1b_hex, 0)
 
@@ -168,11 +161,6 @@ class ReplaceByFeeTest(BitcoinTestFramework):
 
         assert_equal(tx1b_hex, self.nodes[0].getrawtransaction(tx1b_txid))
 
-        # Second node is running mempoolreplacement=0, will not replace originally-seen txn
-        mempool = self.nodes[1].getrawmempool()
-        assert tx1a_txid in mempool
-        assert tx1b_txid not in mempool
-
     def test_doublespend_chain(self):
         """Doublespend of a long chain"""