Update cffconvert.yml

Author: rieder

.github/workflows/cffconvert.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out a copy of the repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Check whether the citation metadata from CITATION.cff is valid
         uses: citation-file-format/cffconvert-github-action@2.0.0