Bug report

mini-css-extract-plugin >= 2.9.0 will prefetch initial css chunk unexpected

Actual Behavior

Expected Behavior

there is no need to prefetch this chunk, because it's a initial chunk

How Do We Reproduce?

git clone https://github.com/992429169/problem-reproduce
cd problem-reproduce
npm i
npm run dev

start a server and visit index.html
i also give a fix patch in this repo

Please paste the results of npx webpack-cli info here, and mention other relevant information