Stop using the deceiving continue-on-error

Build jobs appear as green even though they actually fail.
A better approach is to mark jobs as "required" in branch protection.
This way failed jobs are red, but this doesn't prevent the PR from being
merged upon at maintainers' discretion.

Author: pirj

.github/workflows/ci.yml

@@ -18,11 +18,9 @@ jobs:
        include:
          # Edge Rails (7.0) builds >= 2.7
          - ruby: 3.0
-           allow_failure: true
            env:
              RAILS_VERSION: 'main'
          - ruby: 2.7
-           allow_failure: true
            env:
              RAILS_VERSION: 'main'
 
@@ -98,4 +96,4 @@ jobs:
       - run: script/clone_all_rspec_repos
       - run: bundle install --binstubs
       - run: script/run_build
-        continue-on-error: ${{ matrix.allow_failure || false }}
+        continue-on-error: false