Update chainparams for 0.19.9 release

Summary: See title. Testnet blockheight is 1309000, with current tip being 1311807.

Test Plan:
make check
Check these values against your own node(s).

Reviewers: #bitcoin_abc, deadalnix, Fabien, Mengerian

Reviewed By: #bitcoin_abc, Fabien, Mengerian

Subscribers: Mengerian, markblundeberg

Differential Revision: https://reviews.bitcoinabc.org/D3439