Remove ed25519-dalek recommendation

[pinkforest]

• https://github.com/rustsec/advisory-db/pull/1361
• https://github.com/rustsec/advisory-db/issues/1360
• https://github.com/dalek-cryptography/ed25519-dalek/issues/192
• https://github.com/dalek-cryptography/ed25519-dalek/issues/209
• https://github.com/dalek-cryptography/ed25519-dalek/pull/205

[pinkforest]

Looks like new release coming along :partying_face: