[3.13] gh-123110: correct note about _Bool in the struct module docs (GH-123111) (#123126)

gh-123110: correct note about _Bool in the struct module docs (GH-123111)
(cherry picked from commit b0f462d)

Co-authored-by: Sergey B Kirpichev <skirpichev@gmail.com>

Author: miss-islington

Doc/library/struct.rst

@@ -279,9 +279,9 @@ Notes:
 (1)
    .. index:: single: ? (question mark); in struct format strings
 
-   The ``'?'`` conversion code corresponds to the :c:expr:`_Bool` type defined by
-   C99. If this type is not available, it is simulated using a :c:expr:`char`. In
-   standard mode, it is always represented by one byte.
+   The ``'?'`` conversion code corresponds to the :c:expr:`_Bool` type
+   defined by C standards since C99.  In standard mode, it is
+   represented by one byte.
 
 (2)
    When attempting to pack a non-integer using any of the integer conversion