Bump dieghernan/cff-validator from 5.0.1 to 5.1.1

Bumps [dieghernan/cff-validator](https://github.com/dieghernan/cff-validator) from 5.0.1 to 5.1.1.
- [Release notes](https://github.com/dieghernan/cff-validator/releases)
- [Changelog](https://github.com/dieghernan/cff-validator/blob/main/CHANGELOG.md)
- [Commits](dieghernan/cff-validator@54c8e73...d8f8582)

---
updated-dependencies:
- dependency-name: dieghernan/cff-validator
  dependency-version: 5.1.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

.github/workflows/citations.yml

@@ -35,4 +35,4 @@ jobs:
       run: |
         sudo apt-get update && sudo apt-get install -y r-base
     - name: Validate CITATION.cff
-      uses: dieghernan/cff-validator@54c8e737314b948f25c0e5524a9d8ae3f39b207b # v5.0.1
+      uses: dieghernan/cff-validator@d8f85828214016ce6976e740b6e0504c0fdc4dbb # v5.1.1