patch 8.2.2555: Vim9: missing test for 8.2.2553

Problem:    Vim9: missing test for 8.2.2553.
Solution:   Add a simple test.

src/testdir/test_vim9_script.vim

@@ -258,6 +258,8 @@ def Test_block()
     assert_equal(2, inner)
   }
   assert_equal(1, outer)
+
+  {|echo 'yes'|}
 enddef
 
 def Test_block_failure()