release: Add the Ed25519 vagrant insecure key

Both insecure keys, RSA and Ed25519, are required.

Obtained from: https://github.com/hashicorp/vagrant/commit/b40f6e5fdae1113518e9c92f96dfcd364b646ff9
Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/835