vim-patch:8.1.0546: modeline test with keymap fails

Problem:    Modeline test with keymap fails.
Solution:   Check that the keymap feature is available.
4ace6ab7e7

src/nvim/testdir/test_modeline.vim

@@ -44,6 +44,9 @@ func Test_modeline_syntax()
 endfunc
 
 func Test_modeline_keymap()
+  if !has('keymap')
+    return
+  endif
   call writefile(['vim: set keymap=greek :', 'nothing'], 'Xmodeline_keymap')
   let modeline = &modeline
   set modeline