Rename X-Request-ID to X-Correlation-ID
As mentioned in https://gitlab.com/gitlab-org/gitlab-ce/issues/60111, Rails already uses X-Request-Id to track AJAX requests in the performance bar. The LabKit change breaks the performance bar as a result.
As mentioned in https://gitlab.com/gitlab-org/gitlab-ce/issues/60111, Rails already uses X-Request-Id to track AJAX requests in the performance bar. The LabKit change breaks the performance bar as a result.