[Logs UI] Custom panel font sizes don't follow their expected scales

[formgeist]

Kibana version: 8.0.0

Elasticsearch version: 8.0.0

Description of the problem including expected versus actual behavior:

Just noticed this while testing out the UI. Seems like the font-size scales in the customize panel don't follow their expected sizing. Small is i.e. larger than medium.

[elasticmachine]

Pinging @elastic/infrastructure-ui