update workflow to v4

Author: ezrichards

.github/workflows/deploybook.yaml

@@ -33,7 +33,7 @@ jobs:
 
     # Upload the book's HTML as an artifact
     - name: Upload artifact
-      uses: actions/upload-pages-artifact@v2
+      uses: actions/upload-pages-artifact@v4
       with:
         path: "astudentsguide/_build/html"