Revert "Compute the real-time hash target for the next block"
Summary:
This reverts commit rABCccfbdd5df5fe8815b86fc98bd8e163be51dfcd6f.
I landed a previous version by mistake, let's revert this.
Test Plan:
ninja all check-all
Reviewers: #bitcoin_abc, bytesofman
Reviewed By: #bitcoin_abc, bytesofman
Differential Revision: https://reviews.bitcoinabc.org/D16772