luasnip: only add source if not blink.cmp

blink has it's own builtin thing now

modules/plugins/snippets/luasnip/config.nix

@@ -17,7 +17,7 @@ in {
         };
       };
       startPlugins = cfg.providers;
-      autocomplete = {
+      autocomplete = mkIf config.vim.autocomplete.nvim-cmp.enable {
         nvim-cmp.sources = {luasnip = "[LuaSnip]";};
         sourcePlugins = ["cmp-luasnip"];
       };