Test suite: give sysadmins a chance to update OpenPGP keys before failing

Follow-up on !370 (merged) and reverts #19219 (closed).

Since sysadmin#17816 (closed), sysadmins "get a warning when expiration is about to occur within 60 days (critical after 30)". So let's give them a month to update the key, after which (worst case, if they don't notify us earlier) we still have a month to import it after this Cucumber scenario starts failing.