[test] only run feature_rbf.py once

There is no need to run this test twice with --descriptors and
--legacy-wallet, as it doesn't ever use the wallet.

test/functional/test_runner.py

@@ -231,8 +231,7 @@ BASE_SCRIPTS = [
     'rpc_getblockfrompeer.py',
     'rpc_invalidateblock.py',
     'feature_utxo_set_hash.py',
-    'feature_rbf.py --legacy-wallet',
-    'feature_rbf.py --descriptors',
+    'feature_rbf.py',
     'mempool_packages.py',
     'mempool_package_onemore.py',
     'rpc_createmultisig.py',