Docs: Add missing markup to Argument Clinic docs (pythonGH-106876)

(cherry picked from commit ff5f94b)

Co-authored-by: Erlend E. Aasland <[email protected]>
Co-authored-by: Ezio Melotti <[email protected]>
Co-authored-by: Serhiy Storchaka <[email protected]>

Author: 3 people