netbird: update to 0.60.8 (breaking change)

netbird: update to 0.60.8 (breaking change)

Changelog: https://github.com/netbirdio/netbird/releases/tag/v0.60.8

This is the first `netbird` release that introduces a breaking change[1].
Therefore, versions after the `0.60.x` will not be backported to
OpenWrt 24.10. They will be backported to OpenWrt 25.12, because that
release has not been officially launched yet.

By default netbird now creates/updates[2]
`/etc/ssh/ssh_config.d/99-netbird.conf` for use with `openssh-client`.
OpenWrt uses `dropbear`, and this behavior may cause storage wear.
This behavior has been disabled with `NB_DISABLE_SSH_CONFIG="1"`[3] in the
init file.

[1]: https://forum.netbird.io/t/netbird-v0-60-0-released/334#p-610-upgrade-compatibility-notes-4
[2]: https://docs.netbird.io/manage/peers/ssh#native-ssh-clients-open-ssh
[3]: https://github.com/netbirdio/netbird/blob/v0.60.8/client/ssh/config/manager.go#L167-L172

Signed-off-by: Wesley Gimenes <redacted>