fix: update icon usage in tray guide, closes tauri-apps#796 (tauri-apps#870)

* fix: update icon usage in tray guide, closes tauri-apps#796

* Update docs/guides/features/system-tray.md

Author: amrbashir

docs/guides/features/system-tray.md

@@ -187,10 +187,10 @@ fn main() {
 
 #### Updating tray icon
 
-Note that `tauri::Icon` must be a `Path` variant on Linux, and `Raw` variant on Windows and macOS.
+Note that you need to add `icon-ico` or `icon-png` feature flag to the tauri dependency in your Cargo.toml in order to be able to use `Icon::Raw`
 
 ```rust
-app.tray_handle().set_icon(tauri::Icon::Raw(include_bytes!("../path/to/myicon.ico"))).unwrap();
+app.tray_handle().set_icon(tauri::Icon::Raw(include_bytes!("../path/to/myicon.ico").to_vec())).unwrap();
 ```
 
 [template image]: https://developer.apple.com/documentation/appkit/nsimage/1520017-template?language=objc