OBS repo for Ubuntu 18.04 signing key is expired

[AltoAvenue]

When attempting to run apt update after adding the OBS repo for Ubuntu 18.04, I get

W: GPG error: http://download.opensuse.org/repositories/home:/madsciencecoder:/shticker-book-rewritten/xUbuntu_18.04  Release: The following signatures were invalid: EXPKEYSIG 665DFDAEC2A9F49B home:madsciencecoder OBS Project <home:[email protected]>
E: The repository 'http://download.opensuse.org/repositories/home:/madsciencecoder:/shticker-book-rewritten/xUbuntu_18.04  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