patch 8.2.1734: Vim9: cannot use a funcref for a closure twice

Problem:    Vim9: cannot use a funcref for a closure twice.
Solution:   Instead of putting the funcref on the stack use a growarray on the
            execution context.
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index e6f40cc..a6fba4c 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -1367,7 +1367,7 @@
     enddef
     Func()
   END
-  CheckScriptFailure(lines, 'Multiple closures not supported yet')
+  CheckScriptSuccess(lines)
 enddef
 
 def Test_sort_return_type()