Update chainparams

Summary:
Reviewer note: I ran the script from D3732 to grab these values. Rather than the chainwork matching
the assume valid block, it will more closely match the current chain tip chainwork.

Test Plan:
make check
Verify against your own nodes.

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D3742