Wrap the Parquet type conversions in inline code

Bare `<->` in a `CHANGELOG.md` entry is copied verbatim into the
generated `docs/resources/changelogs/oss/2026.mdx`, where MDX reads `<-`
as the start of a JSX tag and fails to parse the page. `Validate
docs.json` then reports the navigation entry as a missing file.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>