Reopened: Embed metrics in issue chart tooltip styling is inconsistent compared to dashboard

This is a non-foss clone of this previously solved issue: gitlab-foss#65063 (closed)

Embed metrics in issue chart tooltip styling is inconsistent compared to dashboard

As seen from the screenshots, the chart tooltip styling is a little off when the metrics are embedded in an issue. The styling of our markdown is quite deeply nested, so it is quite likely that is the reason for the styling inconsistency.

Reproduction link (monitor team only): https://gitlab.com/jivanvl/test-node-project/issues/2

This was caused by the prometheus-graph-embed class being renamed to metrics-embed.