ci_template: mark the manifest job as not allowed to fail

With gitlab 13.12 the behavior of jobs that depend of manual jobs changes, and they are considered skipped by default.

But in our pipeline we want to enforce that the whole pipeline runs and succeds and the manual status is only there to reduce CI load.

For more details see:

https://about.gitlab.com/blog/2021/05/20/dag-manual-fix/