skip skip-notify warning on Win (#362)

src/main.rs

@@ -87,12 +87,14 @@ fn run() -> Result<()> {
     debug!("Self Update: {:?}", cfg!(feature = "self-update"));
 
     #[cfg(target_os = "linux")]
+    {
         if config.display_preamble() && !config.skip_notify() {
             print_warning("Due to a design issue with notify-send it could be that topgrade hangs when it's finished.
 If this is the case on your system add the --skip-notify flag to the topgrade command or set skip_notify = true in the config file.
 If you don't want this message to appear any longer set display_preamble = false in the config file.
 For more information about this issue see https://askubuntu.com/questions/110969/notify-send-ignores-timeout and https://github.com/topgrade-rs/topgrade/issues/288.");
         }
+    }
 
     if config.run_in_tmux() && env::var("TOPGRADE_INSIDE_TMUX").is_err() {
         #[cfg(unix)]