Disallow review-deploy job to fail in Frontend and QA MRs

What does this MR do?

Disallows review-deploy job to fail in MRs with Frontend and QA changes. At the moment review-deploy job is allowed to fail and its status is being ignored - so the tests would run (and fail) even when the deployment didn't succeed. Making it blocking ensures needs works as intended for the next qa stage and the tests only run on deploy success.

NB the current Review App deployment success rate is at its highest at 98% - https://app.periscopedata.com/app/gitlab/516343/Quality-Department-KPIs?widget=6721558&udv=0

See gitlab-com/www-gitlab-com#12270 (closed) for more details.

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.