E2E test(project wiki): fix test structure

What does this MR do and why?

Fixes the structure of the project wiki delete page test. It was missing a do..end so the Allure reporting wasn't aligned to the other tests.

I also have a feeling this is why QA Bot is assigning Editor failures to other Create SETs, since it applying the editor tag at the Create level. 🤔 e.g. #386354 (closed)

Screenshot

(Before) It was missing the parent Testing project wiki

How to set up and validate locally

bundle exec rspec qa/specs/features/browser_ui/3_create/project_wiki/project_based_page_deletion_spec.rb

MR acceptance checklist

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