patch 8.2.2308: Vim9: no error when assigning lambda to funcref

Problem:    Vim9: no error when assigning lambda to funcref without return
            value.
Solution:   Default return value to "any". (closes #7629)

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2308,
 /**/
     2307,
 /**/