Pin action versions to stable releases for better stability

Co-authored-by: bact <128572+bact@users.noreply.github.com>

Author: Copilot

.github/workflows/codemeta2cff.yml

@@ -26,10 +26,10 @@ jobs:
         uses: actions/checkout@v6
 
       - name: Generate CITATION.cff from codemeta.json
-        uses: caltechlibrary/codemeta2cff@main
+        uses: caltechlibrary/codemeta2cff@v0.2.0
 
       - name: Validate CITATION.cff
-        uses: dieghernan/cff-validator@main
+        uses: dieghernan/cff-validator@v4
 
       - name: Commit and push updated CITATION.cff
         uses: EndBug/add-and-commit@v9