Explore disabling allowed to fail Staging Ref deployment pipeline

The issue is to track the work that is needed to disable ALLOW_GET_FAILURE: 'true' configuration in Staging Ref deployment pipeline.

With the work done in Improve Staging Ref deployment stability (#350482 - closed), GET deployment is much stable now, however there still could be failures caused by upstream changes or environment instability. If the goal is to disable ALLOW_GET_FAILURE, Staging Ref should switch from gitlab-environment-toolkit:dev to use latest stable release and update it on some cadence.