code diffs look weird

[nt4f04uNd]

diff taken from flutter/flutter#79371

i would expect code diffs to looks the same on all platforms

1. ios dark mode - diffs have light background
2. ios light mode - ok, identical with web
3. android light and dark mode - totally broken and different from web

screenshots

	web	ios	android
dark
light

[brianlovin]

Thank you! I'm filing issues for both the iOS and Android bugs now.