Revert "Add syntax scopes to themes (#25323)" (#25339)

This reverts commit 2f416aebbe74f0bbaafe9b18310ff6025fd61916.

We shouldn't have merged this yet, as it currently breaks syntax
highlighting for some languages that haven't had their requisite changes
merged yet.

We also need to be aware of the impact this will have on downstream
themes.

@chbk We should bundle any changes to the themes with the specific
language highlights that depend on those changes (and if there are
multiple languages that need the same change then pick one language to
come first and then stack the rest of the changes on top of that).

Release Notes:

- Community: This is a revert of
https://github.com/zed-industries/zed/pull/25323, so remove those notes
from the release notes.