Update seeds

Summary:
See title.

Note: Someone is pointing hundreds of IPv6 addresses at a small number of BU nodes.
In order to de-dup these, this patch depends on D4779

Test Plan:

contrib/teamcity/check-seeds.sh main 80
contrib/teamcity/check-seeds.sh test 70

Reviewers: #bitcoin_abc, deadalnix, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D4780