patch 8.2.2798: Vim9: redir to variable with append does not accept an index

Problem:    Vim9: redir to variable with append does not accept an index.
Solution:   Make the appending work.
diff --git a/src/version.c b/src/version.c
index 3547ef4..1420e7b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2798,
+/**/
     2797,
 /**/
     2796,