patch 8.2.2389: test failure on a few systems

Problem:    Test failure on a few systems.
Solution:   Avoid that "char" value is negative.
diff --git a/src/version.c b/src/version.c
index 6d99990..568756b8 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2389,
+/**/
     2388,
 /**/
     2387,