Update chainparams for 0.19.2 release

Summary: Updating only mainnet params since testnet is forked due to May upgrade testing.

Test Plan: Verify these against your own node.

Reviewers: deadalnix, Fabien, Mengerian, #bitcoin_abc

Reviewed By: Fabien, Mengerian, #bitcoin_abc

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2725