Require rspec to pass for rails 8 (#1094)

## Summary

Describe the change and the motivation.

## Checklist

- [ ] Tests added/updated and passing (`bin/ci`).
- [ ] Lint and security checks (`rubocop`, `brakeman`, `bundler-audit`).
- [ ] Documentation updated under `docs/` describing new/changed
functionality.
- [ ] Mermaid diagrams (`docs/*.mmd`) updated to reflect changes.
- [ ] Rendered PNGs regenerated with `bin/render_diagrams` and
committed.
- [ ] For DB changes, included any needed backfills/dedupes and noted
risks.

## Screenshots / Diagrams

If applicable, include screenshots or link to updated diagrams.

## Notes

Anything reviewers should be aware of (migration order, flags, feature
toggles).

Author: rsmithlal

.github/workflows/rubyonrails.yml

@@ -15,7 +15,7 @@ jobs:
             allowed_failure: false   # ✅ required
           - ruby: '3.4.4'
             rails: '8.0.2'
-            allowed_failure: true    # ⚠️ allowed to fail
+            allowed_failure: false   # ✅ required
 
     env:
       RAILS_ENV: test