Rename seed for bitcoinforks.org
Rename seed for bitcoinforks.org

Summary: It appears to have been renamed.

Test Plan:
The following returns results:
```
dig seed-bch.bitcoinforks.org
dig testnet-seed-bch.bitcoinforks.org
```
While the following do not:
```
dig seed-abc.bitcoinforks.org
dig testnet-seed-abc.bitcoinforks.org
```

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D7188

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