patch 8.2.1467: Vim9: :echomsg doesn't like a dict argument

Problem:    Vim9: :echomsg doesn't like a dict argument.
Solution:   Convert arguments like in legacy script. (closes #6717)
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 3b8264f..905deb6 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -2102,6 +2102,9 @@
   execute 'echomsg' (n ? '"true"' : '"no"')
   assert_match('^true$', Screenline(&lines))
 
+  echomsg [1, 2, 3] #{a: 1, b: 2}
+  assert_match('^\[1, 2, 3\] {''a'': 1, ''b'': 2}$', Screenline(&lines))
+
   call CheckDefFailure(['execute xxx'], 'E1001:')
   call CheckDefFailure(['execute "cmd"# comment'], 'E488:')
 enddef