Bump version to 0.19.2

Summary: See title

Test Plan:

ninja
bitcoind --version
bitcoin-qt --version

make
bitcoind --version
bitcoin-qt --version

Reviewers: deadalnix, Fabien, Mengerian, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2692