Update aad_b2c_webview.dart fixing redirect on iOS

Use           onUrlChange instead of onPageFinished based on response from SzczygielDev microsoft#14 (comment)

lib/src/presentation/aad_b2c_webview.dart

@@ -80,14 +80,14 @@ class ADB2CEmbedWebViewState extends State<ADB2CEmbedWebView> {
             // Update loading bar.
           },
           onPageStarted: (String url) {},
+          onUrlChange: (change) {
+            final Uri response = Uri.dataFromString(change.url!);
+            onPageFinishedTasks(change.url!, response);
+          },
           onPageFinished: (String url) {
             setState(() {
               isLoading = false;
             });
-
-            final Uri response = Uri.dataFromString(url);
-            //Check that the user is past authentication and current URL is the redirect with the code.
-            onPageFinishedTasks(url, response);
           },
         ),
       )