refactor!: always close second instances

Always close second instances and remove the ability to to close them manually
we can bring it later if it is needed

examples/vanilla/src-tauri/src/main.rs

@@ -5,12 +5,9 @@
 
 fn main() {
   tauri::Builder::default()
-    .plugin(tauri_plugin_single_instance::init(
-      |argv, cwd, close_new_instance| {
-        println!("{argv:?}, {cwd}");
-        close_new_instance();
-      },
-    ))
+    .plugin(tauri_plugin_single_instance::init(|argv, cwd| {
+      println!("{argv:?}, {cwd}");
+    }))
     .run(tauri::generate_context!())
     .expect("error while running tauri application");
 }