test: pass dustrelayfee=0 option for tests using dust (instead of acceptnonstdtxn=1)

By specifying the `dustrelayfee=0` option instead of the more
generic `acceptnonstdtxn=1`, we can be more specific about what
part of the transaction is non-standard and can be sure that all
other aspects follow the standard policy.

test/functional/wallet_basic.py

@@ -25,7 +25,7 @@ class WalletTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 4
         self.extra_args = [[
-            "-acceptnonstdtxn=1", "-walletrejectlongchains=0"
+            "-dustrelayfee=0", "-walletrejectlongchains=0"
         ]] * self.num_nodes
         self.setup_clean_chain = True
         self.supports_cli = False