patch 9.0.1720: Vim9 class using wrong index for overridden method

Problem: Vim9 class using wrong index for overridden method
Solution: Use correct index for overridden method

closes: #12524
closes: #12813

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>
diff --git a/src/version.c b/src/version.c
index bea47fe..ae9bc87 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1720,
+/**/
     1719,
 /**/
     1718,