Remove line profiler from performance bar

What does this MR do?

1. The output isn't great. It can be hard to find hotspots and, even when you do find them, to find why those are hotspots.
2. It uses some jQuery-specific frontend code which we can remove now that we don't have this any more.
3. It's only possible to profile the initial request, not any subsequent AJAX requests.
4. We plan to add separate profiles in https://gitlab.com/gitlab-org/gitlab-ce/issues/64963 and https://gitlab.com/gitlab-org/gitlab-ce/issues/64868 anyway.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• Documentation created/updated or follow-up review issue created