Fix example runtime hook plugin syntax

Editor assessment

The subject names the exact correction — the runtime hook plugin example's syntax — so the header communicates the docs fix and the defect it cures without the diff, and the docs type fits perfectly. Scope omission does no harm since the subject carries the target. Hygiene is clean: imperative mood, no trailing period, sensible length, and no footer is needed for documentation work. A line on what was syntactically wrong would add a little value, but the subject already locates the problem. Clear, accurate, and publishable: a good example.