Update release signing public key in apt keyring

[emkll]

Status

Ready for review.

Description of Changes

Closes #5274.

Testing

• CI is passing
• Key was properly updated based on the previous keyring update: Update securedrop-keyring package to update signing key expiration date #3752

Deployment

• For the server code, new and existing installs will be handled through apt packages.
• For the Admin code, we will need to upload keys to keyservers and on securedrop.org:
  • Updated to keyservers
  • Updated to securedrop.org

Checklist

If you made changes to the server application code:

• Linting (make lint) and tests (make test) pass in the development container

If you made changes to the system configuration:

• Configuration tests pass

If you made non-trivial code changes:

• I have written a test plan and validated it for this PR

[redshiftzero]

LGTM, thanks!