[style] Night mode font color correction

[bd-dxg]

As shown in the figure below, in dark mode, the'h1 'and'h2' of the font should not be black, which will make the reading experience very bad:

If you can cancel the relevant configuration of'color 'and let the browser adapt, the effect will be better!

Current flow version: latest version Browser used: Edge 125.0.2535 (official version) (64-bit)