bpo-41203: Replace Mac OS X and OS X with macOS (GH-28515) (GH-28523)

Replace old names when they refer to actual versions of macOS.
Keep historical names in references to older versions.

Co-authored-by: Patrick Reader <_@pxeger.com>
(cherry picked from commit 36122e18148c5b6c78ebce1d36d514fd7cf250f5)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index f0f8119..237ca4b 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -2789,7 +2789,7 @@
       String that uniquely identifies the type of the filesystem that
       contains the file.
 
-   On Mac OS systems, the following attributes may also be available:
+   On macOS systems, the following attributes may also be available:
 
    .. attribute:: st_rsize