Fix flaky new_project_spec.rb by scoping within pane

What does this MR do and why?

Fixes flaky ee/spec/features/projects/new_project_spec.rb tests and removes their quarantine.

Root cause

The new project page renders 4 tab panes (#blank-project-pane, #create-from-template-pane, #import-project-pane, #ci-cd-project-pane), each containing its own form with duplicate id="project_name" inputs. The creates a new project in personal namespace test used fill_in(:project_name) without scoping to the active pane, causing Capybara to intermittently select an element from a hidden pane.

Fix

• Scope all form interactions within page.within('#blank-project-pane') for the blank project test
• Remove quarantine wrappers from the two CI/CD for GitHub shared example invocations (those tests already scope within #ci-cd-project-pane and navigate away to the GitHub import page)

How to validate

Run the spec locally:

bundle exec rspec ee/spec/features/projects/new_project_spec.rb

All previously quarantined tests should pass consistently.

Related issues

Related to https://gitlab.com/gitlab-org/quality/test-failure-issues/-/work_items/39604