remove isLightTheme from search path
Created by: camdencheek
This commit rips isLightTheme out of the search path because that option is now ignored by the backend. Instead, the backend now returns CSS-highlighted code, so when the theme changes, we don't need to re-request highlighted code.
This can probably be propagated even higher, but I started hitting uses of it for Monaco, so I stopped when I wasn't confident on the intended behavior.