Remove obsolete seeders

Summary: These seeders have not been maintained for a while, and are no longer fonctioning.

Test Plan:
Drill them to check there is no address returned.
Repeat with the other seeders and check they are OK.

Reviewers: #bitcoin_abc, bytesofman

Reviewed By: #bitcoin_abc, bytesofman

Differential Revision: https://reviews.bitcoinabc.org/D14634