Change translate CI job to only detect if po needs updating

Since we might not have 100% translated po in the repository, checking for complete translation isn't relevant anymore.

I've changed the job to detect outdated .po from the source strings point of view. If any changes is made in debexpo in a string that can be translated but the pot or the po files are not updated, the new translation job will fail.

Note that I've removed the ability for this job to gracefully fail.