Update TW quiz to remove deprecated content

The first question in the quiz refers to the backstage label, which appears to be deprecated:
https://gitlab.com/gitlab-org/gitlab/-/labels?utf8=%E2%9C%93&subscribed=&search=backstage

Plus the link to the handbook no longer works. Therefore, suggest we remove this question & answer altogether, as it doesn't add any value. There is an existing question in the quiz that addresses documentation labels, which seems more appropriate.