[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 39859fcac5)

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

Doc/c-api/arg.rst

@@ -685,6 +685,7 @@ Building values
 
    ``p`` (:class:`bool`) [int]
       Convert a C :c:expr:`int` to a Python :class:`bool` object.
+
       .. versionadded:: 3.14
 
    ``c`` (:class:`bytes` of length 1) [char]