Credentialz.GetPublicKeys comment needs improvement

[haussli]

https://github.com/openconfig/gnsi/blob/main/credentialz/credentialz.proto#L224C50-L226

The comment there is vague. Does this return the host's public keys? All user's public keys? Both? I assume the first; but the comments should be explicit.

Also, "key" stutter here:

gnsi/credentialz/credentialz.proto

Line 144 in 6c656fa

// The CA public key key is used to verify certificates presented by

[morrowc]

agreed, could be much more helpful in the docs departmet :) send text? :)