This still works. Here is your html code on my local instance running Grafana 8.0.2:
There was a lot of work done on the Text Panel between Grafana 6 and 7.
Have you set disable_sanitize_html to true in your configurations? You need to do that starting with v7:
docker run -d -p 3000:3000 "GF_PANELS_DISABLE_SANITIZE_HTML=true" grafana/grafana:8.0.2
NOTE:
The default is false because this setting leaves you more exposed to XSS attacks (see PR for larger discussion)