PEP 596: Add 3.9.12 release (python#2465)

https://docs.python.org/release/3.9.12/whatsnew/changelog.html

Author: hugovk

pep-0596.rst

@@ -80,18 +80,19 @@ Actual:
 - 3.9.9: Monday, 2021-11-15
 - 3.9.10: Monday, 2022-01-14
 - 3.9.11: Wednesday, 2022-03-16
+- 3.9.12: Wednesday, 2022-03-23
 
 Expected:
 
-- 3.9.12: Monday, 2022-05-16 (final regular bugfix release with binary
+- 3.9.13: Monday, 2022-05-16 (final regular bugfix release with binary
   installers)
 
 
 Source-only security fix releases
 ---------------------------------
 
 Provided irregularly on an "as-needed" basis until October 2025,
-starting with 3.9.13.
+starting with 3.9.14.
 
 
 3.9 Lifespan