refactor(nixvim): Change autoformatting method

common/home-manager/nixvim/none-ls.nix

@@ -1,20 +1,6 @@
 { ... }: {
   programs.nixvim.plugins.none-ls = {
     enable = true;
-    settings.on_attach = ''
-      function(client, bufnr)
-        if client.supports_method("textDocument/formatting") then
-          vim.api.nvim_clear_autocmds({ group = augroup, buffer = bufnr })
-          vim.api.nvim_create_autocmd("BufWritePre", {
-            group = augroup,
-            buffer = bufnr,
-            callback = function()
-              vim.lsp.buf.format({ async = false })
-            end,
-          })
-        end
-      end
-    '';
     sources = {
       formatting = {
         black.enable = true;