Updated chainparams for 0.19.4 release

Summary: Per release process. Skipping testnet since it has undergone many forks for upgrade testing.

Test Plan: Compare it against your own node(s).

Reviewers: deadalnix, Fabien, Mengerian, #bitcoin_abc

Reviewed By: Fabien, Mengerian, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D2828