rpc: update RPC help of createpsbt

Update the example wherein the PSBT sends bitcoin to an address instead
of creating an OP_RETURN output. Also, update the RPC description to
reflect the fact that the created transaction is unsigned.

Author: rkrux

src/rpc/rawtransaction.cpp

@@ -1550,13 +1550,15 @@ static RPCHelpMan createpsbt()
 {
     return RPCHelpMan{"createpsbt",
                 "\nCreates a transaction in the Partially Signed Transaction format.\n"
-                "Implements the Creator role.\n",
+                "Implements the Creator role.\n"
+                "Note that the transaction's inputs are not signed, and\n"
+                "it is not stored in the wallet or transmitted to the network.\n",
                 CreateTxDoc(),
                 RPCResult{
                     RPCResult::Type::STR, "", "The resulting raw transaction (base64-encoded string)"
                 },
                 RPCExamples{
-                    HelpExampleCli("createpsbt", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\" \"[{\\\"data\\\":\\\"00010203\\\"}]\"")
+                    HelpExampleCli("createpsbt", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\" \"[{\\\"address\\\":0.01}]\"")
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {