Remove legacy React.render() from the editor

Editor assessment

The subject states the modernization exactly: the legacy React.render call removed from the editor. The fix type suits the deprecation cleanup, and the absent scope is tolerable. No body is present, which is acceptable because the subject names the removed API and its location completely, though the console warnings or breakage motivating it would have been worth a clause. The PR reference is well-formed. Imperative mood, no trailing period, compact length. A precise, self-sufficient cleanup message that needs no diff.