public_keys: Update debian repository key for jenkins
A fresh vagrant up on thyssen vm, apt update won't work, complaining about the
repository not being signed. [1]
This fixes it by installing the latest public key exposed on the repository [2]
[1]
W: GPG error: https://pkg.jenkins.io/debian-stable binary/ Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY FCEF32E745F2C3D5 E: The repository 'https://pkg.jenkins.io/debian-stable binary/ Release' 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.
[2] https://pkg.jenkins.io/debian-stable/
Related to T3770