Use simple quote in runtime::window docs

runtime/src/window.rs

@@ -32,7 +32,7 @@ pub enum Action {
     /// Move the window with the left mouse button until the button is
     /// released.
     ///
-    /// There’s no guarantee that this will work unless the left mouse
+    /// There's no guarantee that this will work unless the left mouse
     /// button was pressed immediately before this function is called.
     Drag(Id),