build(deps): bump redhat-plumbers-in-action/differential-shellcheck

Bumps [redhat-plumbers-in-action/differential-shellcheck](https://github.com/redhat-plumbers-in-action/differential-shellcheck) from 5.4.0 to 5.5.1.
- [Release notes](https://github.com/redhat-plumbers-in-action/differential-shellcheck/releases)
- [Changelog](https://github.com/redhat-plumbers-in-action/differential-shellcheck/blob/main/docs/CHANGELOG.md)
- [Commits](redhat-plumbers-in-action/differential-shellcheck@cc6721c...5fa026e)

---
updated-dependencies:
- dependency-name: redhat-plumbers-in-action/differential-shellcheck
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/tests.yml

@@ -30,7 +30,7 @@ jobs:
 
       - id: ShellCheck
         name: Differential ShellCheck
-        uses: redhat-plumbers-in-action/differential-shellcheck@cc6721c45a8800cc666de45493545a07a638d121  # v5.4.0
+        uses: redhat-plumbers-in-action/differential-shellcheck@5fa026e4797665181a0f7c6fa4a73c09348ae78c  # v5.5.1
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
         if: github.event_name == 'pull_request'