[3.10] gh-93738: Documentation C syntax (Use `c:struct`) (GH-97772) (#97893)

Use `c:struct`
(cherry picked from commit a0f5599aac2037da715d09733e0a83a9cba7c37a)

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>