[Reply] Enable predictive back (#1540)

Enable predictive back in the Reply sample

Author: trambui09

Reply/app/src/main/AndroidManifest.xml

@@ -19,6 +19,7 @@
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/Theme.Reply"
+        android:enableOnBackInvokedCallback="true"
         tools:targetApi="31">
         <activity
             android:name=".ui.MainActivity"