Decouple updating chainparams from automated commits pipeline

Summary: See title.

Test Plan:

bitcoind
bitcoind -testnet
COMMIT_TYPE=dummy ./automated-commits.sh -p HEAD ./patch-recipes/update-chainparams.sh
git show    # verify a new commit with chainparams updated

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D7500