patch 8.1.0811: too many #ifdefs

Problem:    Too many #ifdefs.
Solution:   Graduate FEAT_MBYTE, the final chapter.
diff --git a/src/testdir/test_arabic.vim b/src/testdir/test_arabic.vim
index 17e925e..bc31db7 100644
--- a/src/testdir/test_arabic.vim
+++ b/src/testdir/test_arabic.vim
@@ -2,7 +2,7 @@
 " NOTE: This just checks if the code works. If you know Arabic please add
 " functional tests that check the shaping works with real text.
 
-if !has('arabic') || !has('multi_byte')
+if !has('arabic')
   finish
 endif