vim-patch:8.1.0811: too many #ifdefs

Problem:    Too many #ifdefs.
Solution:   Graduate FEAT_MBYTE, the final chapter.
30276f2beb

src/nvim/testdir/test_digraph.vim

@@ -479,9 +479,6 @@ endfunc
 
 func Test_show_digraph_cp1251()
   throw 'skipped: Nvim supports ''utf8'' encoding only'
-  if !has('multi_byte')
-    return
-  endif
   new
   set encoding=cp1251
   call Put_Dig("='")

src/nvim/testdir/test_plus_arg_edit.vim

@@ -10,10 +10,6 @@ function Test_edit()
 endfunction
 
 func Test_edit_bad()
-  if !has('multi_byte')
-    finish
-  endif
-
   " Test loading a utf8 file with bad utf8 sequences.
   call writefile(["[\xff][\xc0][\xe2\x89\xf0][\xc2\xc2]"], "Xfile")
   new

src/nvim/testdir/test_search.vim

@@ -1053,7 +1053,7 @@ func Test_search_Ctrl_L_combining()
     " ' ̇' U+0307 Dec:775 COMBINING DOT ABOVE ̇ /\%u307\Z "\u0307"
     " ' ̣' U+0323 Dec:803 COMBINING DOT BELOW ̣ /\%u323 "\u0323" 
   " Those should also appear on the commandline
-  if !has('multi_byte') || !exists('+incsearch')
+  if !exists('+incsearch')
     return
   endif
   call Cmdline3_prep()