patch 8.1.0811: too many #ifdefs

Problem:    Too many #ifdefs.
Solution:   Graduate FEAT_MBYTE, the final chapter.
diff --git a/src/testdir/test_spell.vim b/src/testdir/test_spell.vim
index 1230c20..76ad12e 100644
--- a/src/testdir/test_spell.vim
+++ b/src/testdir/test_spell.vim
@@ -135,10 +135,8 @@
   set enc=cp1250 spell spelllang=en
   call assert_match("^\nfile: .*/runtime/spell/en.ascii.spl\n$", execute('spellinfo'))
 
-  if has('multi_byte')
-    set enc=utf-8 spell spelllang=en
-    call assert_match("^\nfile: .*/runtime/spell/en.utf-8.spl\n$", execute('spellinfo'))
-  endif
+  set enc=utf-8 spell spelllang=en
+  call assert_match("^\nfile: .*/runtime/spell/en.utf-8.spl\n$", execute('spellinfo'))
 
   set enc=latin1 spell spelllang=en_us,en_nz
   call assert_match("^\n" .