fix CRPCCommand args in rpcwallet.cpp
fix CRPCCommand args in rpcwallet.cpp

Summary:
While backporting [[https://github.com/bitcoin/bitcoin/pull/19994 | core#19994]], I ran into two failing assertions:
  - our version of `getrawchangeaddress` does not have an "address_type" argument
  - the "hexstring" for `signrawtransactionwithwallet` has a typo

Test Plan: `ninja all check-all`

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10340

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