patch 9.0.0156: giving E1170 only in an expression is confusing

Problem:    Giving E1170 only in an expression is confusing.
Solution:   Give E1170 for any "#{ comment". (closes #10855)
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 98a4590..3199ac3 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -2668,8 +2668,12 @@
       'vim9script',
       '# something',
       '#something',
-      '#{something',
+      '#{{something',
       ])
+  v9.CheckScriptFailure([
+      'vim9script',
+      '#{something',
+      ], 'E1170:')
 
   split Xfile
   v9.CheckScriptSuccess([