(deps): Bump dieghernan/cff-validator from 4 to 5

Bumps [dieghernan/cff-validator](https://github.com/dieghernan/cff-validator) from 4 to 5.
- [Release notes](https://github.com/dieghernan/cff-validator/releases)
- [Changelog](https://github.com/dieghernan/cff-validator/blob/main/CHANGELOG.md)
- [Commits](dieghernan/cff-validator@v4...v5)

---
updated-dependencies:
- dependency-name: dieghernan/cff-validator
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/ci-md.yml

@@ -71,6 +71,6 @@ jobs:
       - name: B4) Validate CITATION.cff (if present)
         # WHY: Ensure CITATION.cff is well-formed without making it mandatory.
         if: ${{ steps.detect_citation.outputs.present == 'true' }}
-        uses: dieghernan/cff-validator@v4
+        uses: dieghernan/cff-validator@v5
         with:
           citation-path: CITATION.cff # WHY: Be explicit about the file validated.