fix github action

Author: josephlim94

.github/workflows/docs.yml

@@ -58,7 +58,7 @@ jobs:
 
       - name: Upload artifact
         if: github.ref == 'refs/heads/master'
-        uses: actions/upload-pages-artifact@v2
+        uses: actions/upload-pages-artifact@v4
         with:
           path: ./site