Update seeds.

Summary: Removed clients that are not up to date with the lastest upgrade. That reduces the numer of seeds, but these are good seeds :)

Test Plan:

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Reviewers: #bitcoin_abc, jasonbcox, deadalnix

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2678