disable language command in macOS for now

Due to packaging issue, nvim version 0.7.2 for macOS does not have
`:language` command built in, see also neovim/neovim#19127.

core/globals.vim

@@ -37,7 +37,9 @@ let g:mapleader = ','
 let g:vimsyn_embed = 'l'
 
 " Use English as main language
-language en_US.utf-8
+if !g:is_mac
+  language en_US.utf-8
+endif
 
 " use filetype.lua instead of filetype.vim
 let g:do_filetype_lua = 1