patch 8.2.1028: Vim9: no error for declaring buffer, window, etc. variable

Problem:    Vim9: no error for declaring buffer, window, etc. variable.
Solution:   Give an error.  Unify the error messages.

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1028,
 /**/
     1027,
 /**/