fix: typo in window’s set_subtitle fn (#123)

src/appkit/window/mod.rs

@@ -205,7 +205,7 @@ impl<T> Window<T> {
     /// underlying window. When this property is an empty string, the system removes the subtitle
     /// from the window layout. Allocates and passes an `NSString` over to the Objective C runtime.
     /// Does nothing when less than version 11.
-    pub fn set_subtittle(&self, subtitle: &str) {
+    pub fn set_subtitle(&self, subtitle: &str) {
         if !os::is_minimum_version(11) {
             return;
         }