Remove use of apt-key from debian/ubuntu instructions.

[Clockwork-Muse]

apt-key is deprecated in recent versions of Debian/Ubuntu, in favor of placing the keys in directories (and using the signed-by directive).

[rhatdan]

LGTM @lsm5 @TomSweeneyRedHat PTAL

[lsm5]

@Clockwork-Muse thanks for the PR, let me give this a quick spin and report back.

[lsm5]

@Clockwork-Muse I noticed this after running your steps and doing an apt update:

Err:5 https://download.opensuse.org/repositories/devel:kubic:libcontainers:unstable/xUbuntu_22.04  InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 4D64390375060AA4
Reading package lists... Done
W: GPG error: https://download.opensuse.org/repositories/devel:kubic:libcontainers:unstable/xUbuntu_22.04  InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 4D64390375060AA4
E: The repository 'https://download.opensuse.org/repositories/devel:kubic:libcontainers:unstable/xUbuntu_22.04  InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Did you see this too? I'm not sure if it's the steps mentioned or some issue with the Kubic repo itself. And fwiw, running the old steps does show me a deprecation message along with: gpg: no valid OpenPGP data found. so it's quite likely the kubic repo itself is busted.

[Clockwork-Muse]

@lsm5 - Instructions were downloading the keys to the wrong (dangerous) directory from the original instruction source. Try again.

[lsm5]

@Clockwork-Muse great, thanks a lot for the update. Please squash commits and we're good to merge :)

[Clockwork-Muse]

@lsm5 - Done