Chart thresholds don't scale for multiple series
Thresholds in area and line charts work well when the chart has single series. For multiple series, the passed thresholds props seem to be generating thresholds lines/areas for every series present on the chart.
This will cause multiple threshold lines/areas drawn on the chart and will result in bloated markup and jank.
The API to accept threshold should be updated so that it is restricted to a single series.
getThresholdConfig in https://gitlab.com/gitlab-org/gitlab-ui/-/blob/master/src/components/charts/area/area.vue#L107