[docs] Unpleasant initial UI update for dark mode

[rnike]

Duplicates

• I have searched the existing issues

Latest version

• I have tested the latest version

Current behavior 😯

The site initially displays light mode and then updates to dark mode, bringing pain to my eyes.

record.mp4

Expected behavior 🤔

Initial UI render should be in the correct mode

Steps to reproduce 🕹

Steps:

1. set the site to the dark mode
2. close the site
3. reopen the site

Context 🔦

The issue always happens when entering the site, often when refreshing.

The issue will not appear on doc running with yarn doc:dev, it is probably related to SSR (not quite sure).

Your environment 🌎

npx @mui/envinfo

  Don't forget to mention which browser you used.
  Output from `npx @mui/envinfo` goes here.

[siriwatknp]

Duplicate of #15588