Fix nixvim warning re: web-devicons

```
trace: warning: Nixvim: `plugins.web-devicons` was enabled automatically because the following plugins are enabled.
This behaviour is deprecated. Please explicitly define `plugins.web-devicons.enable` or alternatively
enable `plugins.mini.enable` with `plugins.mini.modules.icons` and `plugins.mini.mockDevIcons`.
plugins.telescope
plugins.bufferline
```

modules/home/neovim/nixvim.nix

@@ -21,6 +21,7 @@
   plugins = {
 
     # UI
+    web-devicons.enable = true;
     lualine.enable = true;
     bufferline.enable = true;
     treesitter.enable = true;