patch 8.2.2567: Vim9: no error if variable is defined for existing function

Problem:    Vim9: no error if variable is defined for existing function.
Solution:   Check if name isn't already in use. (closes #7897)

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2567,
 /**/
     2566,
 /**/