[noise] Using X25519 keypair obtained by Ed25519 conversion

[David Wong]

>From this Golang code your public key is incorrect:
https://gist.github.com/mimoo/1af93fe436c75511b737eddd9fe763bb

calculated public key:
5b3e994f771a950c6ae29bb7f8ae0593c46d4a73312c15db3436b485468bbb6d
     given public key:
26100e941bdd2103038d8dec9a1884694736f591ee814e66ae6e2e2284757136