Update seeds

Summary:
While splitting the seeds between BCHN and BCHA chains is still being worked on,
it's best that we update the seeds anyway post-upgrade to improve peering.

Test Plan:

check-seeds.sh main 80
check-seeds.sh test 70

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D8657