Fix variable naming in StackBasedNavigation.md (#3210)

Sources/ComposableArchitecture/Documentation.docc/Articles/StackBasedNavigation.md

@@ -122,7 +122,7 @@ struct RootView: View {
       path: $store.scope(state: \.path, action: \.path)
     ) {
       // Root view of the navigation stack
-    } destination: { state in
+    } destination: { store in
       // A view for each case of the Path.State enum
     }
   }