test: Remove from_node from create_self_transfer* MiniWallet helpers

The from_node argument is no longer used as of commit
a55606c3bd

test/functional/mempool_unbroadcast.py

@@ -40,7 +40,7 @@ class MempoolUnbroadcastTest(BitcoinTestFramework):
             wallet_tx_hsh = node.sendtoaddress(addr, 0.0001)
 
         # generate a txn using sendrawtransaction
-        txFS = self.wallet.create_self_transfer(from_node=node)
+        txFS = self.wallet.create_self_transfer()
         rpc_tx_hsh = node.sendrawtransaction(txFS["hex"])
 
         # check transactions are in unbroadcast using rpc