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_utf8_comparisons.vim b/src/testdir/test_utf8_comparisons.vim
index f3c86b4..3431226 100644
--- a/src/testdir/test_utf8_comparisons.vim
+++ b/src/testdir/test_utf8_comparisons.vim
@@ -92,3 +92,5 @@
   call feedkeys("gg0g~ap", "tx")
   call assert_equal(["ABCD", "", "defg"], getline(1,3))
 endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab