Merge pull request #403 from stan-dev/dependabot/github_actions/actions/upload-artifact-6

Bump actions/upload-artifact from 5 to 6

Author: jgabry

.github/workflows/test-coverage.yaml

@@ -55,7 +55,7 @@ jobs:
 
       - name: Upload test results
         if: failure()
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@v6
         with:
           name: coverage-test-failures
           path: ${{ runner.temp }}/package