"certificate has expired" for openSUSE Leap 15.5

[thomasmerz]

When trying to update anything on OpenSUSE it fails with this error:

$ zypper lu
Retrieving repository 'google-chrome' metadata ...............................................................................................[done]
Building repository 'google-chrome' cache ....................................................................................................[done]
Retrieving repository 'iridium' metadata ....................................................................................................[error]
Repository 'iridium' is invalid.
[iridium|https://downloads.iridiumbrowser.de/openSUSE_Leap_15.5/] Failed to retrieve new repository metadata.
History:
 - [|] Error trying to read from 'https://downloads.iridiumbrowser.de/openSUSE_Leap_15.5/'
 - Download (curl) error for 'https://downloads.iridiumbrowser.de/openSUSE_Leap_15.5/content':
   Error code: Curl error 60
   Error message: SSL certificate problem: certificate has expired
Please check if the URIs defined for this repository are pointing to a valid repository.
Warning: Skipping repository 'iridium' because of the above error.
Some of the repositories have not been refreshed because of an error.