rpc: Remove duplicate name and argNames from CRPCCommand
Summary:
This is a backport of core#20012 [3/3]
https://github.com/bitcoin/bitcoin/pull/20012/commits/fa04f9b4ddffc5ef23c2ee7f3cc72a7c2ae49204
Depends on D10760
Test Plan: ninja all check-all
Reviewers: #bitcoin_abc, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D10761