build(deps): bump third_party/syntax-highlighting

Bumps [third_party/syntax-highlighting](https://github.com/KDE/syntax-highlighting) from `856e111` to `934c375`.
- [Commits](KDE/syntax-highlighting@856e111...934c375)

---
updated-dependencies:
- dependency-name: third_party/syntax-highlighting
  dependency-type: direct:production
...

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