fix(remote_config, android): make onCancel accept nullable arguments to avoid crash on hot restart (#17569)

Author: SelaseKay

packages/firebase_remote_config/firebase_remote_config/android/src/main/kotlin/io/flutter/plugins/firebase/firebaseremoteconfig/FirebaseRemoteConfigPlugin.kt

@@ -206,9 +206,9 @@ class FirebaseRemoteConfigPlugin
       })
   }
 
-  override fun onCancel(arguments: Any) {
+  override fun onCancel(arguments: Any?) {
     // arguments will be null on hot restart, so we will clean up listeners in didReinitializeFirebaseCore()
-    val argumentsMap = arguments as Map<String, Any>
+    val argumentsMap = arguments as? Map<String, Any>
       ?: return
     val appName = Objects.requireNonNull(argumentsMap["appName"]) as String