wkd_sync: Ignore keys with SHA-1 self-signature
wkd_sync/archlinux-keyring-wkd-sync: Ignore keys with SHA-1 self-signature (by hardcoding them in a readonly array) so that they will not be synced from WKD. The Arch Linux WKD setup does not contain keys with SHA-1 self-signatures anymore.
Fixes #218 (closed)