wallet, rpc: deprecate settxfee and paytxfee

test/functional/wallet_txn_clone.py

@@ -18,6 +18,9 @@ class TxnMallTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 3
         self.supports_cli = False
+        self.extra_args = [[
+            "-deprecatedrpc=settxfee"
+        ] for i in range(self.num_nodes)]
 
     def skip_test_if_missing_module(self):
         self.skip_if_no_wallet()