Pipeline and environment show pages don't have a page title

Every page should have an appropriate page title, but https://gitlab.com/gitlab-com/www-gitlab-com/pipelines/6717032 and https://gitlab.com/gitlab-com/www-gitlab-com/environments/137 don't.

In line with other pages, the title for https://gitlab.com/gitlab-com/www-gitlab-com/pipelines/6717032 should be #6717032 · Pipelines (even though that doesn't seem every useful), and the title for https://gitlab.com/gitlab-com/www-gitlab-com/environments/137 should be production · Environments.