Remove `broken-ci` dashboard from dashboards.gitlab.net

At https://dashboards.gitlab.net Grafana we have a https://dashboards.gitlab.net/d/RZmTUrSiz/broken-ci dashboard which was an imported version of it equivalent at performance.gitlab.net. It was added to the .BROKEN catalog, since it was using our InfluxDB datasource.

I've created https://dashboards.gitlab.net/d/000000159/ci which is a fresh copy of https://performance.gitlab.net/d/000000159/ci but without the two panels that were using InfluxDB. The broken-ci may be now removed. I would do it myself, but I don't have edit access to that dashboard 😉