patch 8.2.0520: tests are not listed in sorted order

Problem:    Tests are not listed in sorted order.
Solution:   Move test_ex_mode. (Doug Richardson, closes #5889)
diff --git a/src/version.c b/src/version.c
index 6e9f006..b73dd61 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    520,
+/**/
     519,
 /**/
     518,