Fix performance bar thresholds

These were written in seconds but are supposed to be in milliseconds. The total Gitaly time was wrong for the same reason.

I noticed this while working on https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/32344 but you can also see it in production: the second is pretty obvious (0ms / 19 gitaly doesn't look right), and the first is visible in the network inspector.