This RPC was added for testing wallet rebroadcasts. Since we now have a
real test for wallet rebroadcasts, it's no longer needed.
The call in wallet_basic.py can be removed because
wallet_resendwallettransactions.py tests wallet rebroadcast.
https://github.com/bitcoin/bitcoin/pull/15680/commits/f5162458cd3e757ee6bbc7e963b61d365ccc536a
This is a partial backport of Core PR15680