当我更新时，出现此错误：
sudo apt-get update
Hit:1 https://brave-browser-apt-release.s3.brave.com stable InRelease
Hit:3 https://cli.github.com/packages stable InRelease
Hit:4 https://updates.signal.org/desktop/apt xenial InRelease
Hit:5 http://packages.microsoft.com/repos/code stable InRelease
Hit:6 https://dl.google.com/linux/chrome/deb stable InRelease
Hit:7 https://repo.steampowered.com/steam stable InRelease
Hit:8 http://archive.ubuntu.com/ubuntu lunar InRelease
Hit:9 https://deb.nodesource.com/node_19.x kinetic InRelease
Get:10 https://zotero.retorque.re/file/apt-package-archive ./ InRelease [2.153 B]
Get:11 http://archive.ubuntu.com/ubuntu lunar-updates InRelease [90,7 kB]
Hit:12 https://ppa.launchpadcontent.net/ubuntuhandbook1/transmission/ubuntu kinetic InRelease
Get:13 https://packages.element.io/debian default InRelease [3.609 B]
Get:2 https://packages.element.io/debian default InRelease [3.609 B]
Err:13 https://packages.element.io/debian default InRelease
The following signatures were invalid: EXPKEYSIG C2850B265AC085BD riot.im packages <[email protected]>
Hit:14 http://archive.ubuntu.com/ubuntu lunar-backports InRelease
Err:2 https://packages.element.io/debian default InRelease
The following signatures were invalid: EXPKEYSIG C2850B265AC085BD riot.im packages <[email protected]>
Get:15 http://archive.ubuntu.com/ubuntu lunar-security InRelease [90,7 kB]
Reading package lists... Done
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://packages.element.io/debian default InRelease: The following signatures were invalid: EXPKEYSIG C2850B265AC085BD riot.im packages <[email protected]>
W: GPG error: https://packages.element.io/debian default InRelease: The following signatures were invalid: EXPKEYSIG C2850B265AC085BD riot.im packages <[email protected]>
E: The repository 'https://packages.riot.im/debian default 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.
我应该怎么办？