fix deprecated version of actions/upload-artifact: v3 (#22)

Author: F3r-n4nd0

.github/workflows/build-docs.yml

@@ -79,7 +79,7 @@ jobs:
           done
 
       - name: Upload Pages artifact
-        uses: actions/upload-pages-artifact@v2
+        uses: actions/upload-pages-artifact@v3
 
   # Deploy github pages job
   deploy: