ci: set retention on uploaded artifacts

Author: haasonsaas

.github/workflows/diffscope.yml

@@ -91,6 +91,7 @@ jobs:
         if: always() && steps.provider.outputs.configured == 'true'
         uses: actions/upload-artifact@v4
         with:
+          retention-days: 14
           name: diffscope-review-${{ github.event.pull_request.number }}
           path: comments.json
           if-no-files-found: ignore

.github/workflows/eval.yml

@@ -104,6 +104,7 @@ jobs:
         if: ${{ always() && steps.secret-check.outputs.configured == 'true' }}
         uses: actions/upload-artifact@v4
         with:
+          retention-days: 14
           name: eval-reports
           path: |
             eval-current.json