Remove 'antialias' remnants

It never did anything (see `:h hidden-options`).

src/nvim/options.lua

@@ -50,15 +50,6 @@ return {
       varname='p_aleph',
       defaults={if_true={vi=224}}
     },
-    {
-      full_name='antialias', abbreviation='anti',
-      type='bool', scope={'global'},
-      vi_def=true,
-      vim=true,
-      redraw={'everything'},
-      enable_if=false,
-      defaults={if_true={vi=false, vim=false}}
-    },
     {
       full_name='arabic', abbreviation='arab',
       type='bool', scope={'window'},