patch 9.0.0345: error message for list argument could be clearer

Problem:    Error message for list argument could be clearer.
Solution:   Include the argument number. (Yegappan Lakshmanan, closes #11027)
diff --git a/src/testdir/test_method.vim b/src/testdir/test_method.vim
index 22a930c..d31cce1 100644
--- a/src/testdir/test_method.vim
+++ b/src/testdir/test_method.vim
@@ -52,7 +52,7 @@
   call assert_fails("let x = d->insert(0)", 'E899:')
   call assert_true(d->has_key('two'))
   call assert_equal([['one', 1], ['two', 2], ['three', 3]], d->items())
-  call assert_fails("let x = d->join()", 'E714:')
+  call assert_fails("let x = d->join()", 'E1211:')
   call assert_equal(['one', 'two', 'three'], d->keys())
   call assert_equal(3, d->len())
   call assert_equal(#{one: 2, two: 3, three: 4}, d->map('v:val + 1'))