Failure of a job in the test stage prevents the website from being built and deployed

Since #17364 (closed), a failure of any job in the test stage of the CI pipeline prevents the website from being built and deployed:

• Example of issue when APT snapshots are near expiration: https://gitlab.tails.boum.org/tails/tails/-/pipelines/13586
• Example of temporary failure when checking 3rd-party TLS certificates: https://gitlab.tails.boum.org/tails/tails/-/jobs/144185