Update version to 3.8.20.1

Author: i-shenl

Doc/whatsnew/3.8.rst

@@ -2402,3 +2402,8 @@ email
   check if the *strict* paramater is available.
   (Contributed by Thomas Dwyer and Victor Stinner for :gh:`102988` to improve
   the CVE-2023-27043 fix.)
+  
+Notable changes in 3.8.20.1
+===========================
+
+* Upgraded libexpat to 2.6.4 to fix CVE-2024-50602

Include/patchlevel.h

@@ -23,7 +23,7 @@
 #define PY_RELEASE_SERIAL       0
 
 /* Version as a string */
-#define PY_VERSION              "3.8.20"
+#define PY_VERSION              "3.8.20.1"
 /*--end constants--*/
 
 /* Version as a single 4-byte hex number, e.g. 0x010502B2 == 1.5.2b2.