patch 8.2.0790: Vim9: list index not well tested

Problem:    Vim9: list index not well tested.
Solution:   Add a few more tests.
diff --git a/src/version.c b/src/version.c
index 53d69d5..aa03f90 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    790,
+/**/
     789,
 /**/
     788,