patch 8.1.0811: too many #ifdefs

Problem:    Too many #ifdefs.
Solution:   Graduate FEAT_MBYTE, the final chapter.
diff --git a/src/testdir/test_matchadd_conceal_utf8.vim b/src/testdir/test_matchadd_conceal_utf8.vim
index 68792fb..d280c15 100644
--- a/src/testdir/test_matchadd_conceal_utf8.vim
+++ b/src/testdir/test_matchadd_conceal_utf8.vim
@@ -1,5 +1,5 @@
 " Test for matchadd() and conceal feature using utf-8.
-if !has('conceal') || !has('multi_byte')
+if !has('conceal')
   finish
 endif