Fail the devcontainer CI job when rake spec fails

The runCmd is a multi-line bash script with no `set -e`, so a non-zero
exit from `bundle exec rake spec` does not propagate. The script keeps
running, executes `bundle exec rubocop`, and the script's exit code
becomes RuboCop's exit code. As long as RuboCop is clean, GitHub
Actions marks the job green even when rspec is red.

Run 26084989755 hit this: 4 ORA-01805 failures in rake spec, but the
job was reported as success because RuboCop passed.

Add `set -e` so the first non-zero exit aborts the script and surfaces
through the action as a job failure.

Author: yahonda

.github/workflows/devcontainer.yml

@@ -21,6 +21,7 @@ jobs:
         uses: devcontainers/ci@v0.3
         with:
           runCmd: |
+            set -e
             uname -a
             lsb_release -a
             ruby --version