patch 8.1.0811: too many #ifdefs

Problem:    Too many #ifdefs.
Solution:   Graduate FEAT_MBYTE, the final chapter.
diff --git a/src/testdir/test_cmdline.vim b/src/testdir/test_cmdline.vim
index 9a4ccd1..4dcda85 100644
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -582,7 +582,7 @@
 endfunc
 
 func Test_cmdline_overstrike()
-  let encodings = has('multi_byte') ? [ 'latin1', 'utf8' ] : [ 'latin1' ]
+  let encodings = ['latin1', 'utf8']
   let encoding_save = &encoding
 
   for e in encodings
@@ -601,11 +601,9 @@
     call assert_equal('"ab0cd3ef4', @:)
   endfor
 
-  if has('multi_byte')
-    " Test overstrike with multi-byte characters.
-    call feedkeys(":\"テキストエディタ\<home>\<right>\<right>ab\<right>\<insert>cd\<enter>", 'xt')
-    call assert_equal('"テabキcdエディタ', @:)
-  endif
+  " Test overstrike with multi-byte characters.
+  call feedkeys(":\"テキストエディタ\<home>\<right>\<right>ab\<right>\<insert>cd\<enter>", 'xt')
+  call assert_equal('"テabキcdエディタ', @:)
 
   let &encoding = encoding_save
 endfunc