Fix "fonts test HTML document" styles (#4718)
Fix "fonts test HTML document" styles (#4718)

Needed some update after we made htm.css obsolete and
use epub.css instead.
pazos/koreader,NiLuJe/koreader,koreader/koreader,mwoz123/koreader,mihailim/koreader,NiLuJe/koreader,Frenzie/koreader,Frenzie/koreader,houqp/koreader,poire-z/koreader,Hzj-jie/koreader,koreader/koreader,poire-z/koreader,Markismus/koreader