Add travel_to for ai spec

What does this MR do and why?

Failed job: https://jihulab.com/gitlab-cn/gitlab/-/jobs/12815303#L6596

Why

为什么没有改动 main-jh，突然报错了：

因为 代码中设置了 2024-2-15 固定时间，超过此时间后测试的逻辑发生变化了。

相关 Upstream MR：https://gitlab.com/gitlab-org/gitlab/-/merge_requests/138523

1) admin/application_settings/general.html.haml instance-level code suggestions settings when on self managed env with license with :code_suggestions feature available when turn on feature flag admin_ai_access_setting renders code suggestions form
     Failure/Error: expect(rendered).to have_field('application_setting_instance_level_code_suggestions_enabled')
       expected to find field "application_setting_instance_level_code_suggestions_enabled" that is not disabled but there were no matches
     # ./jh/spec/views/admin/application_settings/general.html.haml_spec.rb:40:in `block (7 levels) in <main>'
     # ./spec/spec_helper.rb:435:in `block (3 levels) in <top (required)>'

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