patch 9.0.1200: AppVeyor builds with an old Python version

Problem:    AppVeyor builds with an old Python version.
Solution:   Switch from Python 3.8 to 3.11. (Christopher Plewright,
            closes #11814)
diff --git a/src/version.c b/src/version.c
index 2b472d3..9427081 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1200,
+/**/
     1199,
 /**/
     1198,