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)
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index c26f2af..9f19ebd 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -1508,7 +1508,7 @@
       'delfunc g:NotExist'], 'E700:')
 enddef
 
-def RefFunc(Ref: func(string): string): string
+def RefFunc(Ref: func(any): any): string
   return Ref('more')
 enddef