patch 8.2.1432: various inconsistencies in test files

Problem:    Various inconsistencies in test files.
Solution:   Add modelines where they were missing.  Use Check commands instead
            of silently skipping over tests.  Adjust indents and comments.
            (Ken Takata, closes #6695)
diff --git a/src/testdir/test_vim9_expr.vim b/src/testdir/test_vim9_expr.vim
index 09792ef..c87f2b2 100644
--- a/src/testdir/test_vim9_expr.vim
+++ b/src/testdir/test_vim9_expr.vim
@@ -2009,3 +2009,5 @@
   call CheckDefFailure(["echo Func0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789()"], 'E1011:')
   call CheckDefFailure(["echo doesnotexist()"], 'E117:')
 endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab