light: use placeholder foreground for ansi white

[mkhl]

in the light theme, the ansi whites are illegible on the default terminal background
(yes sadly some commands do stuff like that)

this change reuses the placeholder foreground color for the whites to fix that

[mkhl]

output of esbuild --help
before:

and after:

[mkhl]

hmm actually i think #CCCCCC has better contrast against other colors 🤔