This reverts commit 1caf672904.
Otherwise public key signature is regenerated each time the key is
loaded and test `key::tests::test_load_self_existing` which loads the
key twice fails when two loads happen on different seconds.
Closes#5976
ASCII armored keys can be easily generated with `sq key generate` and
used to encrypt and decrypt test messages with `sq` and `gpg` without
converting them to binary using `base64 -d` first.
