Fix `project#pages_available?` refactor broken JH own business logic

What does this MR do and why?

Related issue: #3630 (closed)

Fix project#pages_available? refactor broken JH own business logic

Broken by upstream MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/133216

Effected files:

• lib/api/helpers.rb
• lib/sidebars/projects/menus/deployments_menu.rb

Reference discussion: !2055 (merged)

Request upstream prepend_mod MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/133568