Update generate-pdf.yml

Author: wyfcyx

.github/workflows/generate-pdf.yml

@@ -40,7 +40,7 @@ jobs:
         make latexpdf
         
     - name: Upload PDF to Artifacts
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v4
       with:
         name: tutorial-pdf
         path: build/latex/rcore-tutorial-book-v3.pdf