theme: Remove default syntax colors (#11980)

This PR removes the default syntax colors from the theme.

With the changes in #11911 these colors could leak through if the theme
didn't provide a value for that syntax color.

Removing them gives themes a clean slate to work with.

Release Notes:

- N/A
79098671e6Marshall Bowers committed on 5/17/2024, 2:54:51 PM· committed by GitHubparent8631280
3 files changedLine totals unavailable