Remove support for deprecated IPNS records v1

[lidel]

Part of https://github.com/ipfs/specs/issues/314, corresponding Kubo issue: https://github.com/ipfs/kubo/issues/9240

Support for extensible records (and v2 signature) was added in 2021 (https://github.com/ipfs/js-ipns/pull/121). JS-IPFS is producing and preferring updated v2 IPNS records by default, but if no v2 is found, it will still accept deprecated v1 for backward-compatibility during the transition period.

A year later, we should remove fallback support for validating v1 signatures and ignore them instead.