ci: update upload-artifact

Author: Cloudef

.github/workflows/ci.yml

@@ -45,7 +45,7 @@ jobs:
            run: sudo apt-get install doxygen
          - name: make doxygen
            run: make doxygen
-         - uses: actions/upload-artifact@v2
+         - uses: actions/upload-artifact@v4
            with:
               name: docs
               path: html