Remove config argument from blockToJSON
Summary:
Was added in "move-only" diff D717.
It is not used anymore since introduction of TxToUniv in D2499.
Depends on D3014
Test Plan: make check
Reviewers: #bitcoin_abc, deadalnix, Fabien
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D3070