[3.14] Fix versionadded directive rendering in c-api/arg.rst (GH-135199) (#135207)

Fix versionadded directive rendering in c-api/arg.rst (GH-135199)
(cherry picked from commit 39859fcac5c8335ca9c1bddc5945a7d3e934aebc)

Co-authored-by: Rafael Fontenelle <rffontenelle@users.noreply.github.com>