patch 8.2.4484: Vim9: some error messages are not tested

Problem:    Vim9: some error messages are not tested.
Solution:   Add a few more test cases.  Delete dead code.
diff --git a/src/version.c b/src/version.c
index 9ba8bb9..c64bd83 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4484,
+/**/
     4483,
 /**/
     4482,